Proceedings Volume 8923

Micro/Nano Materials, Devices, and Systems

James Friend, H. Hoe Tan
Proceedings Volume 8923

Micro/Nano Materials, Devices, and Systems

James Friend, H. Hoe Tan
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 6 January 2014
Contents: 31 Sessions, 116 Papers, 0 Presentations
Conference: SPIE Micro+Nano Materials, Devices, and Applications 2013
Volume Number: 8923

Table of Contents


Table of Contents

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  • Front Matter: Volume 8923
  • Fabrication I
  • Solar I
  • Nanomaterials I
  • Bio I
  • Photonics I
  • Materials I
  • Microfluidics I
  • Plasmonics I
  • Bio II
  • Photonics II
  • Solar II
  • Plasmonics II
  • MEMS I
  • Photonics III
  • Metrology/Characterisation
  • Microfluidics II
  • Solar III
  • Electronics
  • Plasmonics III
  • Microfludics III
  • Solar IV
  • Nanomaterials IV
  • Bio IV
  • Photonics IV
  • Materials II
  • Fabrication III
  • Photonics V
  • Nanomaterials V
  • Poster Session
Front Matter: Volume 8923
Front Matter: Volume 8923
This PDF file contains the front matter associated with SPIE Proceedings Volume 8923, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.
Fabrication I
Black-Si as a platform for sensing
G. Gervinskas, P. Michaux, G. Seniutinas, et al.
The nano-textured surface of black silicon can be used as a surface-enhanced Raman scattering (SERS) substrate. Sputtered gold films showed increasing SERS sensitivity for thicknesses from 10 up to 300 nm, with sensitivity growing nonlinearly from around 50 nm until saturation at 500 nm. At 50 nm, a cross over from a discontinuous to a fully percolated film occurs as revealed by morphological and electrical measurements. The roughness of the Au coating increases due to formation of nanocrystallites of gold. Structural characterization of the black- Si needles and their surfaces revealed presence of silicon oxide and fluoride. The sharpest nano-needles had a tip curvature radius of ~10 nm. SERS recognition of analyte using molecular imprinted gels with tetracycline molecules of two different kinds is demonstrated.
Development of silicon optics for an integrated micro-optical system-on-a-chip
David C. Ng, Sasikaran Kandasamy, Efstratios Skafidas
Development of silicon-based passive optical components such as reflectors, waveguides, and beam splitters coupled with active elements such as light emitters and detectors enable miniaturisation of a low-cost system-on-a-chip sensing device. In this work, we investigate methods to fabricate passive silicon elements on a chip. We use a combination of wet and dry etching techniques to realise angled and vertical sidewalls normal to the surface of a silicon wafer, respectively. For wet etching, we used Triton-X, a surfactant, added to an alkaline solution TMAH as the etchant. This allows perfect 45° inclined sidewalls to be fabricated. Dry etching using DRIE is to be performed on the reverse-side of the same wafer to realize through-hole vias with straight vertical sidewalls. A final Au metal layer can then be coated onto the sidewalls to realize reflective surfaces. Photolithography masks used in the wet and dry etch processes were designed and fabricated. By careful alignment of these masks using a mask aligner, we can fabricate a combination of inclined and vertical sidewalls to build optical reflectors and beam splitters with complex geometries. When integrated with active Si-optical devices, a fully integrated micro-optical system-on-a-chip can be realised.
Solar I
Enhanced photovoltaic performance of dye-sensitized solar cell using composite photoanode on 3D electrode
Chiew Keat Lim, Hui Huang, Man Siu Tse, et al.
For dye-sensitized solar cell (DSSC), an efficient transport of electron from the dye sensitizer through the mesoporous oxide layer and to be collected by electrode is crucial for high photovoltaic conversion efficiency. In this work, two novel approaches were developed in DSSC fabrication to improve the overall photovoltaic performance. The concurrent improvement in the charge transport property and light harvesting efficiency was achieved by incorporating N-doped TiO2 in the mesoporous TiO2 layer of the photoanode. These N-doped TiO2 (TiNxOy) was formed by using the single step thermal oxidation of Titanium Nitride (TiN) nanomaterials. At the same time, the 3D electrode with SnO2 nanorods grown on the FTO glass using plasma enhanced chemical vapor deposition (PECVD) system was used to enhance the charge collection efficiency. By combining these two approaches simultaneously, the DSSC with composite TiNxOy-TiO2 photoanode on SnO2 nanorods 3D electrode was successfully fabricated and characterized. As compared to the standard DSSC, an overall increment of 28 % in the conversion efficiency was achieved. Higher incident photon-current conversion efficiency (IPCE) values were also obtained, specifically for the region 400 – 500 nm due to the cosensitization effect of N-doped TiO2. Efficient transfer of electron due to the decrease in charge transfer resistance at the mesoporous oxide/dye/electrolyte interface was observed from electrochemical impedance spectroscopy (EIS) measurement. With the use of SnO2 nanorods, the adhesion between the mesoporous TiO2/FTO was enhanced and the transit time of a photogenerated electron through the mesoporous layer before being collected at the FTO electrode was significantly reduced by 50 %.
Mixed metal oxides for dye-sensitized solar cell using zinc titanium layered double hydroxide as precursor
Jianqiang Liu, Yaowei Qin, Liangji Zhang, et al.
Mixed metal oxides (MMO) are always obtained from layered double hydroxide (LDH) by thermal decomposition. In the present work, a zinc titanium LDH with the zinc titanium molar ratio of 4.25 was prepared by urea method and ZnO-based mixed oxides were obtained by calcining at or over 500°C. The MMO was used as electrodes for dye sensitized solar cell (DSSC). The cells constructed by films of prepared composite materials using a N719 as dye were prepared. The efficiency values of these cells are 0.691%, 0.572% and 0.302% with MMO prepared at 500, 600 and 700°C, respectively.
Direct transfer of solar radiation to high temperature applications
This paper reviews the different methods of directly transferring solar radiation from concentrated solar collectors to medium to high temperature thermal absorbers, at temperatures ranging from 100 to 400°. These methods are divided into four main categories associated with the radiation transfer medium: optical fibres, photonic crystal fibres, metal waveguides and light guides. The reviewed methods are novel compared to most rooftop solar concentrators that have a receiver and a thermal storage unit coupled by heat transfer fluids. Bundled optical fibres have the capability of transferring concentrated solar energy across the full wavelength spectrum with the maximum optical efficiency. In this study two different types of optical bundle, including hard polymer cladding silica (HPCS) and polymer clad silica (PCS) fibres are introduced which offer a broad spectrum transmission range from 300 to 1700 nm, low levels of losses through attenuation and the best resistance to heating. These fibres are able to transmit about 94% of the solar radiation over a distance of 10 m. The main parameters that determine the overall efficiency of the system are the concentration ratio, the acceptance angle of the fibres, and the matching of the diameter of the focus spot of the concentrator and the internal diameter of the fibre. In order to maximize the coupling efficiency of the system, higher levels of concentration are required which can be achieved through lenses or other non-imaging concentrators. However, these additional components add to the cost and complexity of the system. To avoid this problem we use tapered bundles of optical fibres that enhance the coupling efficiency by increasing the acceptance angle and consequently the coupling efficiency of the system.
Nanomaterials I
Fluorescent emission in different silicon carbide polytypes
S. Castelletto, B. C. Johnson, I. Aharonovich, et al.
Silicon carbide (SiC) is a widely used material in several industrial applications such as high power electronics, light emitting diodes, and in research application such as photo-voltaic and quantum technologies. As nanoparticles it can be synthetised in many sizes and different polytypes from 200 nm down to 1 nm. In the form of quantum dots they are used as optical biomarkers, and their emission, occurring from the blue to the orange spectral region, is based on quantum confinement effect. In this work we report on emission in the red and near infrared in different SiC polytypes, specifically in 4H, 6H and 3C. In 4H SiC the red visible emission yielded non classical light attributed to an intrinsic defect, identified as a carbon-antisite vacancy pair. Similar spectral emission was observed in 3C SiC bulk and nanoparticles, also yielding very bright single photon emission. Emission in the far red has been observed in homogeneous hetero-structure in SiC tetrapods.
Graphene-polymer multilayer heterostructure for terahertz metamaterials
Zaiquan Xu, Caiyun Chen, Steve Qing Yang Wu, et al.
The optical response and plasmon coupling between graphene sheets for graphene/polymer multilayer heterostructures with controlled separation were systematically investigated. Anomalous transmission of light was experimentally observed in mid-infrared range. The position of the broad passband in the transmission spectra was observed to red-shift with the increase of the number of layers.
Density functional theory calculations of phenol-modified monolayer silicon nanosheets
Michelle J. S. Spencer, Tetsuya Morishita, Michael R. Bassett
Silicon nanosheets are one of most exciting recent discoveries, being a two-dimensional form of silicon that is only nanometers thick, with large lateral dimensions. A single atomic layer silicon nanosheet is known as silicene and can be grown with different surface terminations. It has been shown previously that organo-modified silicene can be synthesised with phenyl groups covalently bonded to both sides of the nanosheet, with hydrogen atoms terminating the undercoordinated silicon atoms. In this work, we use density functional theory calculations and ab initio molecular dynamics simulations to determine the effect of hydroxyl (OH) group substitutions on the phenyl-modified silicene. Different positions of the OH groups on the phenyl rings were modelled including ortho-, meta- and para- substituted positions. We found that the meta-substituted position was favoured, followed by the para- then ortho- substituted positions. Our ab initio MD simulations showed that the phenol groups will freely rotate on the nanosheet, aligning so as to form hydrogen bonds between adjacent phenol groups. The unique properties of this material could be useful for future electronic device applications.
Bio I
Challenges in specificity and collection efficiency for integrated optical biosensors
Andrea M. Armani, Simin Mehrabani, Ashley J. Maker, et al.
While many new label-free optical sensing techniques are focusing on increasing the sensitivity or decreasing the limit of detection, the balance between sensitivity, specificity and collection efficiency are critical, particularly for detection in complex media. For example, although high Q optical resonant cavities are inherently sensitive, the collection efficiency of these devices is quite poor, particularly when compared to sensors with larger active sensing areas. By optimizing all three parameters, even further advancements in sensing technologies are possible.
Nanosensors for next generation drug screening
Sridhar K. Kannam, Matthew T. Downton, Natalie Gunn, et al.
One promising path for future drug screening technologies is to examine the binding of ligands to target proteins at the single molecule level by passing them through nanometer sized pores and measuring the change in pore current during translocation. With the aim of evaluating such technologies we perform virtual experiments on the translocation of proteins through silicon nitride nanopores. These simulations consist of large scale, fully atomistic models of the translocation process that involve steering a test protein through the nanopore on a timescale of tens of nanoseconds. We make a comparison between theoretically expected and simulated values of the current drop that is seen when the protein occupies the pore. Details of the stability of the protein and the preservation of its function as measured by its secondary and tertiary structure will be presented to validate both the simulation results and the fundamental design of the proposed device. Finally, the results will be placed in the context of experimental work that combines nanofabrication and microuidics to create a high throughput, low cost, drug screening device.
Photonics I
Third-order optical nonlinearity in BDN dye encapsulated polymer matrix induced by nanosecond laser pulses
Devendra Mohan, Purnima Arya, Anil Kumar
The present work focuses on the study of nonlinear optical properties of bis(4-dimethylaminodithiobenzyl)-nickel (BDN) dye encapsulated in poly-methylmethacrylate (PMMA) matrix. The Z-scan measurements are carried out using nanosecond laser pulses of Nd: YAG laser at 532nm wavelength with maximum energy of 200mJ per pulse as excitation source. The nonlinearity in terms of excited state absorption (ESA) has been discussed. A switching from saturation absorption (SA) to reverse saturation absorption (RSA) is reported from absorptive study in samples of different thickness. The nonlinear parameters viz. nonlinear absorption coefficient ( β ), nonlinear index of refraction ( n2 ) and third-order nonlinear susceptibility ( χ3 ) are calculated. The thermal diffusivity that provides the rate at which a temperature disturbance travels within the medium is used to estimate thermal conductivity of solid-state polymeric samples. The nonlinear refractive index gradient is determined in terms of thermo-optic coefficient ( dn/dT ).The observed nonlinearity is attributed to laser induced acoustic motion with rise time of thermal lens of nanosecond order that agrees well with literature reported earlier. The study shows that BDN dye encapsulated polymers are excellent material for stable optical limiting and pulse shaping applications.
Translation interference pattern in nano-scale precision by phase control based on spatial light modulator
Jie Ma, Yongchun Zhong, Zhe Chen, et al.
A technique of using phase control method to translate the interference pattern was demonstrated. By using a liquid crystals spatial light modulator (LC-SLM) to regulate the phase of beams, real-time dynamic translations of the patterns were achieved. The translation accuracy is up to 10 nm experimentally. This technique can apply to any kind of multi-beam interference pattern and has no limits in translation accuracy and direction, theoretically.
Constructing microstructures using the optical trapping map of dielectric spheres
Micro-particle self-assembly provides an insight into the dynamics of particles in a well-understood force environment, interactions between particles, and processes where particles themselves modify the force environment. Various ways have been reported on creating microparticle assembly in optical traps. Yet the basis to understanding the nature of the assembly is to first comprehend trapping of a single sphere in a focused Gaussian laser beam. For spherical dielectric particles that are to be manipulated by a focused Gaussian laser beam, the axial trapping efficiency of this is a function of (i) the particle radius r, (ii) the ratio of the refractive index of particle over the medium, and (iii) the numerical aperture of the delivered light beam. From a comprehensive simulation conducted, we uncovered optical trapping regions in the 3D parameter space forming an iso-surface landscape with ridge-like contours. Using specific points in the parameter space, we drew attention to difficulties in using the trapping efficiency and stiffness metrics in defining how well particles are drawn into and held in the trap. An alternative calculation based on the maximum forward and restoration values of the trapping efficiency in the axial sense, called the trapping quality, was proposed. We also discuss the possibility of coupling optical trapping with other physical methods, notably capillary forces, in order to achieve effective microparticle assembly.
Materials I
Hydride VPE: the unexpected process for the fast growth of GaAs and GaN nanowires with record aspect ratio and polytypism-free crystalline structure
Yamina André, Agnès Trassoudaine, Geoffrey Avit, et al.
Hydride Vapor Phase Epitaxy (HVPE) makes use of chloride III-Cl and hydride V-H3 gaseous growth precursors. It is known as a near-equilibrium process, providing the widest range of growth rates from 1 to more than 100 μm/h. When it comes to metal catalyst-assisted VLS (vapor-liquid-solid) growth, the physics of HVPE growth is maintained: high dechlorination frequency, high axial growth rate of nanowires (NWs) up to 170 μm/h. The remarkable features of NWs grown by HVPE are the untapered morphology with constant diameter and the stacking fault-free crystalline phase. Record pure zinc blende cubic phase for 20 μm long GaAs NWs with radii of 10 and 5 nm is shown. The absence of wurtzite phase in GaAs NWs grown by HVPE whatever the diameter is discussed with respect to surface energetic grounds and kinetics. Ni assisted, Ni-Au assisted and catalyst-free HVPE growth of wurtzite GaN NWs is also addressed. Micro-photoluminescence spectroscopy analysis revealed GaN nanowires of great optical quality, with a FWHM of 1 meV at 10 K for the neutral donor bound exciton transition.
In situ monitoring of resistivity and carrier concentration during molecular beam epitaxy of topological insulator Bi2Se3
Jack Hellerstedt, J. H. Chen, Dohun Kim, et al.
Bismuth selenide (Bi2Se3) is a three-dimensional strong topological insulator of particular interest due to its relatively large bulk band gap (300 meV), single set of topologically non-trivial surface states, and layered van der Waals structure. However, there are outstanding problems in isolating the surface states of interest from bulk (trivial) conduction: this problem is frequently attributed to doping from selenium vacancies, and atmospheric exposure. To address these questions, we have constructed a system capable of growing thin film bismuth selenide by van der Waals epitaxy with the additional capability to do real time, in situ transport measurements, specifically resistivity and Hall carrier density. Post growth cooling to 15 K, and controlled exposure to atmospheric dopants is possible without breaking vacuum. We have demonstrated in-situ electrical measurements of resistivity and Hall effect which allow monitoring of the charge carrier density and mobility during growth as well as post-growth without breaking vacuum.
Effect of compositional gradient on mechanical properties in aluminum/duralumin multi-layered clad structures
Hideaki Tsukamoto, Yoshiki Komiya, Hisashi Sato, et al.
This study aims to investigate the effect of compositional gradient on nano-, micro- and macro-mechanical properties in aluminum (A1050)/ duralumin (A2017) multi-layered clad structures fabricated by hot rolling. Such multilayered clad structures are possibly adopted to a new type of automobile crash boxes to effectively absorb the impact forces generated when automobiles having collisions. 2- and 6-layered clad structures with asymmetric lay-ups from one side of aluminum to another side of duralumin have been fabricated, which have been suffering three different heattreatments such as (1) as-rolled (no heat-treatment), (2) annealed at 400°C and (3) homogenized at 500°C followed by water quenching and aging (T4 heat treatment). For nano- and micro-scale mechanical properties proved by nanoindentation, higher hardness and elastic modulus correspond to higher Cu content at the interface in annealed and aged samples. For macro-scale mechanical properties, internal friction of 2-layered clad structures is higher than that of 6-layered clad structures in any heat-treatment samples. Deep drawing formability of annealed samples is considerably high compared to as-rolled and aged ones.
Electron spin resonance spectroscopy of high purity crystals at millikelvin temperatures
Warrick G. Farr, Daniel L. Creedon, Maxim Goryachev, et al.
Progress in the emerging field of engineered quantum systems requires the development of devices that can act as quantum memories. The realisation of such devices by doping solid state cavities with paramagnetic ions imposes a trade-off between ion concentration and cavity coherence time. Here, we investigate an alternative approach involving interactions between photons and naturally occurring impurity ions in ultra-pure crystalline microwave cavities exhibiting exceptionally high quality factors. We implement a hybrid Whispering Gallery/Electron Spin Resonance method to perform rigorous spectroscopy of an undoped single-crystal sapphire resonator over the frequency range 8{19 GHz, and at external applied DC magnetic fields up to 0.9 T. Measurements of a high purity sapphire cooled close to 100 mK reveal the presence of Fe3+, Cr3+, and V2+ impurities. A host of electron transitions are measured and identified, including the two-photon classically forbidden quadrupole transition (Δms = 2) for Fe3+, as well as hyperfine transitions of V2+.
Composite anode La0.8Sr0.2MnO3 impregnated with cobalt oxide for steam electrolysis
Shisong Li, Jigui Cheng, Kui Xie, et al.
Oxygen-ion conducting solid oxide electrolyzer (SOE) has attracted a great deal of interest because it converts electrical energy into chemical energy directly. The oxygen evolution reaction (OER) is occurred at the anode of solid oxide electrolyzer as the O2- being oxidized and form O2 gas, which is considered as one of the major cause of overpotentials in steam electrolyzers. This paper investigates the electrolysis of steam based on cobalt oxide impregnated La0.8Sr0.2MnO3 (LSM) composite anode in an oxide-ion-conducting solid oxide electrolyzer. The conductivity of LSM is studied versus temperature and oxygen partial pressure and correlated to the electrochemical properties of the composite electrodes in symmetric cells at 800 °C. Different contents of Co3O4 (wt.1%, 2%, 4%, 6%, 8%, 10%) were impregnated into LSM electrode and it was found that the polarization resistance (Rp) of symmetric cells gradually improved from 1.16 Ω•cm2 (LSM) to 0.24 Ω•cm2 (wt.10%Co3O4-LSM). Steam electrolysis based on LSM and wt.6%Co3O4-LSM anode electrolyzers are tested at 800°C and the AC impedance spectroscopy results indicated that the Rp of high frequency process significantly decreased from1.1 Ω•cm2 (LSM) to 0.5 Ω•cm2 (wt.6%Co3O4-LSM) under 1.8V electrolysis voltage and the Rp of low frequency process decreased from 14.9 Ω•cm2 to 5.7 Ω•cm2. Electrochemical catalyst Co3O4 can efficiently improve the electrode and enhance the performance of high temperature solid oxide electrolyzer.
Microfluidics I
Small volume particulate and non-particulate sample collection for fluidic systems
Brandon H. Cheong
In fluidic systems, it is often desirable to collect samples in the hydrated state at one location. Most methods devised to do this are often complex. In this work, we present a method that uses a simple squeeze flow. We demonstrate its use in the collection of cells (algal cells), particulates (microbeads and fluorescent nanobeads) and non-particulates (EGFP). This fluidic system is amenable for high content microscopy. An assumption often made is that objects being observed are fixed spatially and are sufficiently populated. Without the ability to collect, this can lead to the need for searching through multiple field of views (FOVs). We report that the generation of a squeeze flow by the circular coverslip onto a liquid sample allows for objects to be acquired at the rim regions of the circular coverslip. By using a coverslip of 13 mm diameter and sample volumes between 2 μL and 4 μL, the coverslip was completely filled without any excess flow beyond its outer rim. Furthermore, sample compression speeds between 100 μm/s and 1000 μm/s did not change the effect of the object collection outcome. A comparison was made between manually placing the coverslip on the liquid sample by hand and using a motorised translator to generate the squeeze flow and in both cases, similar outcomes were obtained. Quantitative measurements and image analysis confirmed that all the objects investigated had been displaced and relocated at the rim regions of the coverslip at a very high degree and ready to be collected. Also by using a metal cylinder and probe tip, pre-concentration of material was achieved.
Plasmonics I
Simulation of the gap plasmon coupling with a quantum dot
Active control of plasmon propagation via coupling to Quantum Dots (QDs) is a hot topic in nano-photonic research. When a QD is excited it acts like a dipole emitter. If this excited QD is placed near a metallic waveguide structure, it can decay either radiatively into bulk electromagnetic radiation, non-radiatively into heating of the metal or, of interest to this project, into a plasmon mode (γpl). By altering the position of the QD it is possible to optimise the decay into the plasmon mode.

In this paper we present a system with a QD placed within the vicinity of a single mode Gap Plasmon Waveguide (GPW). First, we constructed a 2D finite element modelling simulation to find γpl using COMSOL MULTIPHYSICS for symmetric GPW structures with varying width (w) of the gap and distance of the QD to the waveguide surface (d). We then constructed a 3D model to calculate total rate of spontaneous emission of a QD (γtot) and determine spontaneous emission β factor, which is the ratio between γpl and all possible decay channels. It is shown that the decrease in width of the gap results in much larger β factor. As the gap width decreases, fraction of modal power in the metal increases slowing down the plasmon mode resulting in an enhancement in coupling efficiency. The optimized β factor for a square metallic slot waveguide is estimated up to 80%.
Polarization effect and emission control in asymmetric cross-shaped slot antennas surrounded with periodic corrugations
A. Djalalian-Assl, J. Cadusch, T. D. James, et al.
We discuss progress in the development of asymmetric cross-shaped plasmonic antennas based on resonant nanoscale apertures surrounded by surface corrugations. By tailoring the aperture and the surrounding surface, we show directionality and polarization control of transmitted light.
Bio II
Water-soluble benzylidene cyclopentanone photosensitizers for two-photon excited photodynamic therapy
Yanyan Fang, Hongyou Zhao, Qianli Zou, et al.
A series of benzylidene cyclopentanone photosensitizers modified by polyethylene glycol, carboxylate anionic or pyridyl cationic groups with gradient lipid-water partition coefficients were reported. Detailed characterization and systematic studies of these photosensitizers, including their linear and nonlinear photophysical properties, in vitro photodynamic therapy (PDT) and two-photon excited PDT (2PE–PDT) activities were conducted and compared with a clinical drug PSD-007 (a mixture of porphyrins). Three of them exhibited appropriate lipid-water partition coefficients, high reactive oxygen yields, large two-photon absorption cross-section and low dark toxicity under therapy dosage, could be absorbed efficiently by liver hepatocellular HepG2 cells and presented strong PDT and 2PE-PDT activity by in vitro cell experiments. Furthermore, in vivo tumor experiments were carried out on BALB/c mouse models using B3 as the photosensitizer. The results showed that the tumor growth could be effectively suppressed by B3 under 2PE-PDT. This work demonstrated the feasibility of using a simple molecular structure to construct high efficient photosensitizers for 2PE-PDT.
Effects of laser-exposed gold nanorods on biochemical pathways of neuronal cells
Chiara Paviolo, John W. Haycock, Paul R. Stoddart, et al.
Gold nanorods with citrate termination, poly(4 - styrenesulfonic acid) coating and silica coating were taken up by NG108 - K15 neuronal cells. This process proved to generate reactive oxygen species (ROS) and activate the nuclear factor κ -B (NF - κB). However, subsequent exposure to laser light at the plasmon resonance wavelength showed no long term cell damage or ROS / NF- κB activation. Interestingly, monitoring of intracellular Ca2+ signaling showed evidence of photo - generated transients without alteration of other normal cell functions. These results suggest new opportunities for peripheral nerve regeneration treatments and for infrared neural stimulation.
Influence of surface acoustic waves induced acoustic streaming on the kinetics of electrochemical reactions
Sabrina Tietze, Josefine Schlemmer, Gerhard Lindner
The kinetics of electrochemical reactions is controlled by diffusion processes of charge carriers across a boundary layer between the electrode and the electrolyte, which result in a shielding of the electric field inside the electrolyte and a concentration gradient across this boundary layer. In accumulators the diffusion rate determines the rather long time needed for charging, which is a major drawback for electric mobility. This diffusion boundary can be removed by acoustic streaming in the electrolyte induced by surface acoustic waves propagating of the electrode, which results in an increase of the charging current and thus in a reduction of the time needed for charging. For a quantitative study of the influence of acoustic streaming on the charge transport an electropolishing cell with vertically oriented copper electrodes and diluted H3PO4-Propanol electrolytes were used. Lamb waves with various excitation frequencies were exited on the anode with different piezoelectric transducers, which induced acoustic streaming in the overlaying electrolytic liquid. An increase of the polishing current of up to approximately 100 % has been obtained with such a set-up.
Laser measurements of bacterial endospore destruction from shock waves
Petros P. Lappas, A. Daniel McCartt, Sean D. Gates, et al.
The effects of shock waves on bioaerosols containing endospores were measured by combined laser absorption and scattering. Experiments were conducted in the Stanford aerosol shock tube for post-shock temperatures ranging from 400 K to 1100 K. Laser intensity measurements through the test section of the shock tube at wavelengths of 266 and 665 nm provided real-time monitoring of the morphological changes (includes changes in shape, structure and optical properties) in the endospores. Scatter of the visible light measured the integrity of endospore structure, while absorption of the UV light provided a measure of biochemicals released when endospores ruptured. For post-shock temperatures above 750 K the structural breakdown of Bacillus atrophaeus (BA) endospores was observed. A simple theoretical model using laser extinction is presented for determining the fraction of endospores that are ruptured by the shock waves. In addition, mechanisms of endospore mortality preceding their disintegration due to shock waves are discussed.
Photonics II
Characterization of optical polarization converters made by femtosecond laser writing
Christiaan J. de Jong, Alireza Lajevardipour, Mindaugas Gecevičius, et al.
Recently, new types of silica polarization converters fabricated by femtosecond lasers have been introduced. These devices use spatially arranged nanogratings found under certain femtosecond laser exposure conditions in fused silica to create arbitrary polarization states by shaping spatially and locally the retardance of an incoming beam. Using this principle, radial and azimuthal polarization converters were demonstrated. These devices make use of a large density of femtosecond laser spots, introducing localized defects, affecting the performance of the converter. To optimize the writing and the post-processing annealing step of these kind of devices, here we introduce a novel fluorescence lifetime imaging microscope (FLIM) working with deep UV (240-280 nm) wavelength excitations. Specifically, we demonstrate the potential of this technique and more generally, how it can be used for characterizing a variety of femtosecond laser induced modifications in fused silica. This UV-FLIM can be used with micro-fluidic and bio-samples to characterize temporal characteristics of fluorescence.
The application of carbon nanotubes in mode locked fiber laser
Zhenhua Yu, Yonggang Wang, Yanrong Song
We demonstrate a mode locked fiber laser based on single wall carbon nanotubes. The mode locking is achieved by the evanescent field interaction of the propagating light with a single wall carbon nanotubes saturable absorber in a microfiber. The pulse width is 114fs. The maximum average output power is 21mW. The center of the wavelength is 1556nm with 26nm spectral width. The repetition rate is 111.6MHz. Keywords: Ultrafast lasers; Mode locked lasers; carbon nanotubes.
Comparison of Al2O3 nano-overlays deposited with magnetron sputtering and atomic layer deposition on optical fibers for sensing purposes
Mateusz Śmietana, Tomasz Drążewski, Piotr Firek, et al.
In this work we compare effects of thin (<300 nm) aluminum oxide (Al2O3) deposition using advanced physical (Magnetron Sputtering - MS) and chemical (Atomic Layer Deposition – ALD) vapor deposition methods on optical fibers. We investigate an influence of the process parameters on optical properties of the nano-films deposited with MS. In order to investigate the properties of the films directly on the fibers, we induced long-period fiber grating (LPG) in the fiber prior the deposition. Thanks to LPG sensitivity to thickness and optical properties of the overlays deposited on the fiber, we are able to monitor Al2O3 nano-overlay properties. Moreover, we investigate an influence of the overlays deposited with both the methods on LPG-based refractive index (RI) sensing. We show and discuss tuning of the RI sensitivity by proper selection of both thickness and optical properties of the Al2O3 nano-overlays.
Solar II
Heterogeneous nano-particle array for the realization of the hot carrier solar cell
A hot carrier solar cell device that consists of heterogeneous nano-particle arrays has been proposed. It has been demonstrated that such array has good properties both as a light absorber and as a carrier conductor. The photo-generated hot carrier populations can be potentially retained due to the strong acoustic impendence between the component nano-particles, which localizes the lattice vibrational energy. The electronic and phononic properties of the nano-particles have demonstrated the potential of generating a hot carrier population. It has been demonstrated that by modulating the structure of the array, it is possible to maintain a fine electrical conductivity while strongly block the lattice heat conductivity. This helps to minimize the entropy generation during the energy conversion process, providing possibilities of realizing the high-efficiency hot carrier solar cell.
Solution processing of next-generation nanocrystal solar cells
J. van Embden, A. S. R. Chesman, N. W. Duffy, et al.
Next-generation solar cells will be fabricated from low-cost and earth abundant elements, using processes that are amenable to printing on a variety of light-weight substrates. The utilization of compositionally and structurally controlled colloidal nanocrystals as building blocks for such devices fulfills these criteria. Our recent efforts in developing kesterite Cu2ZnSnS4 (CZTS) nanocrystals, one of the most promising materials to emerge in this area, enable the deposition of CZTS thin-films directly from a variety of solution-processed methods. Nanocrystalline thin films possess poor electronic properties, which precludes their use in solar cell devices. In order to overcome this, thermal treatment steps under an atmosphere of vaporous selenium are applied to induce large scale crystallite growth and the production of selenized CZTSSe films. This process results in a highly photoactive p-type layer. The n-type cadmium sulfide layer is also deposited from solution using chemical bath deposition. We will discuss each of these accomplishments in detail, highlighting the significant challenges that need to be overcome in order to fabricate working CZTSSe thin film solar cells.
Optical properties and electron dynamics in carbon nanodots
Xiaoming Wen, Shujuan Huang, Gavin Conibeer, et al.
Carbon nanodots (CNDs) have emerged as fascinating materials with exceptional electronic and optical properties, and thus they offer promising applications in photonics, photovoltaics and photocatalysis. Herein we study the optical properties and electron dynamics in CNDs using steady state and time-resolved spectroscopy. The photoluminescence (PL) is determined to originate from both core and surface. The massive surface fluorophores result in a broad spectral fluorescence. In addition to various synthesis techniques, it is demonstrated that the PL of CNDs can be extended from the blue to the near infrared by thermal assisted growth. Directional electron transfer was observed as fast as femtosecond in CND-graphene oxide nanocomposites from CND into graphene oxide. These results suggest CNDs can be promising in many applications.
Plasmonics II
Optoplasmonics: hybridization in 3D
L. Rosa, G. Gervinskas, A. Žukauskas, et al.
Femtosecond laser fabrication has been used to make hybrid refractive and di ractive micro-optical elements in photo-polymer SZ2080. For applications in micro- uidics, axicon lenses were fabricated (both single and arrays), for generation of light intensity patterns extending through the entire depth of a typically tens-of-micrometers deep channel. Further hybridisation of an axicon with a plasmonic slot is fabricated and demonstrated nu- merically. Spiralling chiral grooves were inscribed into a 100-nm-thick gold coating sputtered over polymerized micro-axicon lenses, using a focused ion beam. This demonstrates possibility of hybridisation between optical and plasmonic 3D micro-optical elements. Numerical modelling of optical performance by 3D-FDTD method is presented.
Ultra-compact plasmonic nanoring laser
C.-W. Lee, Q. Wang, G. Singh, et al.
We presented the design of metallic-semiconductor nanolasers based on ring configuration lasing at around 1450 nm wavelength. The design and simulation of the nanolaser are done with 3D body-of-revolution (BOR) finite-differencetime- domain (FDTD) simulator based on a multi-level multi-electron system. Both passive cavity optimization and active laser simulation are carried out. New results are reported, but to be more comprehensive we also review some of our previous results. For the smallest design, which corresponds to one resonance order in the cavity, the total footprint of the nanolaser is only about 0.038 μm2, and the physical device volume and the mode volume are only about 1.1(λ/2n)3 and 0.001(λ/2n)3, respectively, where n is the average index of the gain material. This device by us is the smallest reported to date, to the best of our knowledge. We also design for higher resonance orders that have larger dimensions and better fabrication feasibility, as well as taking into consideration the fabrication tolerances. All these are presented in the paper.
Effect of surfaces on thermoelastic damping of nano-resonators
S. Dixit, M. M. Inamdar, D. N. Pawaskar
The objective of this study is to investigate the role of surfaces on thermoelastic damping of flexural vibrations in nanobeams. In the past, the role of surfaces on thermoelastic damping of a vibrating nanobeam has been discussed by considering only mechanical interaction between surfaces and the rest of bulk without accounting for thermal interaction between them. In this paper we account for heat flow due to conduction between the surface and bulk and a coupled thermo-mechanical heat equation for a thermoelastic surface has been derived. Quality factor of vibrating rectangular nanobeam has been computed using modified thermal boundary conditions for the bulk under adiabatic surface conditions. An expression for surface heat capacity used in modified boundary conditions has been derived using the modified Debye model. A simplified expression for quality factor of thin rectangular nanobeam has been obtained. We note that the quality factor and the frequency at which the maximum dissipation occurs is a function of both mechanical and thermal properties of surface. It has also been noticed that the relative change in thermoelastic dissipation due to surface effect is a function of operating frequency. The present analysis shows that effect of surfaces on quality factor and peak damping frequency increases with decrease in beam thickness. Coupled heat equation for a surface derived in the present work can be used for any general thermoelastic surface.
Cryogenic optical profilometry for the calculation of coefficient of thermal expansion in thin films
Kirsten L. Brookshire, Ramin Rafiei, Mariusz Martyniuk, et al.
This work focuses on the development of a cryogenic optical profilometry system for the measurement of material properties of thin films across a wide temperature range. A cryostat was machined and integrated with a Zygo NewView 600K optical profilometer and vacuum system. Curvature data were taken for a SiNx thin film on a GaAs substrate from 300 K down to 80 K. From the curvature data, the coefficient of thermal expansion was calculated. The cryogenic optical profilometry system was benchmarked with a three beam curvature technique, and demonstrated excellent agreement across the full temperature range from 300 K to 80 K
Photonics III
Measuring the electrical properties of semiconductor nanowires using terahertz conductivity spectroscopy
Hannah J. Joyce, Callum J. Docherty, Chaw-Keong Yong, et al.
Accurately measuring the electronic properties of nanowires is a crucial step in the development of novel semiconductor nanowire-based devices. With this in mind, optical pump–terahertz probe (OPTP) spectroscopy is ideally suited to studies of nanowires: it provides non-contact measurement of carrier transport and dynamics at room temperature. OPTP spectroscopy has been used to assess key electrical properties, including carrier lifetime and carrier mobility, of GaAs, InAs and InP nanowires. The measurements revealed that InAs nanowires exhibited the highest mobilities and InP nanowires exhibited the lowest surface recombination velocity.
THz photomixer with a 40nm-wide nanoelectrode gap on low-temperature grown GaAs
G. Seniutinas, G. Gervinskas, E. Constable, et al.
A terahertz (THz or T-rays) photomixer consisting of a meander type antenna with integrated nanoelectrodes on a low temperature grown GaAs (LT-GaAs) is demonstrated. The antenna was designed for molecular fingerprinting and sensing applications within a spectral range of 0.3-0.4 THz. A combination of electron beam lithography (EBL) and focused ion beam (FIB) milling was used to fabricate the T-ray emitter. Antenna and nanoelectrodes were fabricated by standard EBL and lift-off steps. Then a 40-nm-wide gap in an active photomixer area separating the nanoelectrodes was milled by a FIB. The integrated nano-contacts with nano-gaps enhance the illuminated light and THz electric fields as well as contribute to a better collection of photo-generated electrons. T-ray emission power from the fabricated photomixer chips were few hundreds of nanowatts at around 0.15 THz and tens of nanowatts in the 0.3-0.4 THz range.
Extending device performance in photonic devices using piezoelectric properties
This study focuses on the influence of epi-layer strain and piezoelectric effects in asymmetric GaInAs/GaAlAs action regions that potentially lead to intra-cavity frequency mixing. The theoretical limits for conduction and valence band offsets in lattice-matched semiconductor structures have resulted in the deployment of non-traditional approaches such as strain compensation to extend wavelength in intersubband devices, where strain limits are related to misfit dislocation generation. Strain and piezoelectric effects have been studied and verified using select photonic device designs. Metrics under this effort also included dipole strength, oscillator strength, and offset of energy transitions, which are strongly correlated with induced piezoelectric effects. Unique photonic designs were simulated, modeled, and then fabricated using solid-source molecular beam epitaxy into photonic devices. The initial designs produce "lambda" wavelength, and the introduction of the piezoelectric effect resulted in "lambda/2" wavelength. More importantly, this work demonstrates that the theoretical cutoff wavelength in intersubband lasers can be overcome.
Sound of nano
Jon Aylott, Matt Clark, Leonel Marques, et al.
Ultrasound is widely used for imaging, measurement and diagnostics in the MHz region and is perhaps most familiar as a medical or non-destructive imaging or measurement tool. In the MHz frequency range the wavelength is typically measured in microns and is many times longer than the wavelength of visible light, limiting its resolution to objects much larger than the nano-scale. It is possible to perform ultrasonic imaging and measurement at much higher frequencies, in the GHz region. Here the acoustic wavelength is typically less than that of light permitting the higher resolutions than optical microscopy and the ability to probe micro and nano-scale objects. At these high frequencies ultrasonics has much to offer the nano-world as a powerful diagnostic tool: it could be used in circumstances where optical microscopy, electron microscopy and probe microscopy cannot, such as inside living objects. Despite the potential that ultrasonics offers for imaging and measurement at the micro and nano-scale, performing ultrasonics at the nano-scale is hampered by many problems that render the techniques typically used in the MHz region impractical. In this paper we discuss some of the practical problems standing in the way of nano-ultrasonics and some of the solutions, especially the use of pico-second laser ultrasonics and the development of nano-ultrasonic transducers and their application to ultrasonic imaging inside living cells.
Microfluidics II
Microfluidic devices using thiol-ene polymers
Simon J. M. C. Bou, Amanda V. Ellis
Here, a new polymeric microfluidic platform using off-stoichiometric thiol-ene (OSTE) polymers was developed. Thiolene polymers were chosen as they afford rapid UV curing, low volume shrinkage and optical transparency for use in microfluidic devices. Three different off-stoichiometric thiol-ene polymers with 30% excess allyl, 50% excess thiol and a 90% excess thiol (OSTE Allyl-30, OSTE-50 and OSTE-90, respectively) were fabricated. Attenuated reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and solid-state cross polarisation-magic angle spinning (CP-MAS) nuclear magnetic resonance (NMR) spectroscopy confirmed which functional groups (thiol or allyl) were present in excess in the OSTE polymers. The polymers were shown to have a more hydrophilic surface (water contact angle of 65°± 3) compared to polydimethylsiloxane (water contact angle of 105° ± 5). Testing of the mechanical properties showed the glass transition temperatures to be 15.09 °C, 43.15 °C and, 57.48 °C for OSTE-90, OSTE Allyl-30 and, OSTE-50, respectively. The storage modulus was shown to be less than 10 MPa for the OSTE-90 polymer and approximately 1750 MPa for the OSTE Allyl-30 and OSTE-50 polymers. The polymers were then utilised to fabricate microfluidic devices via soft lithography practices and devices sealed using a one-step UV lamination “click” reaction technique. Finally, gold nanoparticles were used to form gold films on the OSTE-90 and OSTE-50 polymers as potential electrodes. Atomic force microscopy and sheet resistances were used to characterise the films.
A microfluidic platform to study the mechano sensational properties of ion channels
Microfluidic platforms have been widely considered as an enabling technology for studying the ion transport phenomena of cells under precisely controlled shear stresses. Here, we report the application of a unique microfluidic platform to analyze the response of transgenic TRPV4-HEK293 cells in response to different shear stresses and in one field of view. Applying this system, we show the kinetics of calcium signalling at different shear stresses in TRPV4 positive cells and elucidate the threshold of their response. We show that there is direct correlation between the magnitude of shear stress and percentage of cells that are able to sense that level of shear. Further, we show that shear stress-induced elevation in intracellular calcium levels ([Ca2+]i) is through calcium influx from extracellular sources. The results demonstrate that the microfluidic system has unique capabilities for analysis of shear stress on adhesive cells and that it should be amenable to moderate throughput applications.
Solar III
Current density enhancement in inverted nanopyramid textured crystalline silicon solar cell using gold nanoparticles
Senthuran Sivasubramaniam, Dhiraj Kumar, V. B. Golovko, et al.
The surface plasmon resonances induced light coupling is widely recognized as a promising way of enhancing the light absorption in photovoltic devices. This is achieved by enhanced localized electromagnetic field in the vicinity of metal surface or the strong light scattering effects from metal nanoparticles integrated on the front surface of as-fabricated solar cells. In this paper, the colloidal gold nanoparticles(Au NPs), synthesized by modified Turkevich and Frens method, were integrated onto the inverted nanopyramid silicon solar cell via a dip coating method. A 7% increase in short-circuit current density of solar cell was observed for 15 minutes dip coating. As a result, a 4.6% increase in overall efficiency was achieved. However,the dense surface coverage of Au NPs resulted in decreased fill factor.
Ion-beam and plasma etching of a conical-pores photonic crystal for thin-film solar cell
Gediminas Gervinskas, Lorenzo Rosa, Saulius Juodkazis
Conical holes bored in the active layer of a thin-film silicon solar cell by ion-beam lithography (IBL) show increase of effective optical absorption in the underlying silicon active layer. The optical properties are numerically simulated by the 3D finite-difference time-domain method (3D-FDTD), showing wideband increase of the UV, visible, and IR quantum efficiency. An experimental fabrication procedure is developed using IBL for high wide- area repeatability. A further optimization on the cone shapes is performed in order to make fabrication feasible with plasma etching techniques.
Growth of CZTS by co-sputtering and sulfurization for solar cell applications
N. Muhunthan, Om Pal Singh, V. N. Singh
Earth abundant copper-zinc-tin-sulfide (CZTS) is an important class of material for the development of low cost and sustainable thin film solar cells. Fabrications of CZTS thin film is carried out by magnetron co-sputtering the metallic and sulfide targets and post deposition sulfurization. We sputter Cu using DC power and ZnS and SnS using RF power. In order to study its structure properties and to establish the best growth conditions, Raman spectroscopy and Glazing incident XRD analysis were carried out. These studies indicated that the grown CZTS film have a kesterite with good crystallinity and strong preferential orientation along (112) plane. SEM analysis revealed a homogeneous, compact surface morphology and large grains throughout the thickness of the film. The grown CZTS film demonstrated an optical absorption coefficient higher than ~ 6x104cm-1 and optical band gap of 1.45 eV. The sheet resistance, carrier concentration, mobility and activation energy of the CZTS film are 2.52 kΩ, 1.86 x 1018 cm-3, 1.92 cm2V-1s-1, and 37.8 meV, respectively. These optical and electrical properties are suitable for thin film solar cell fabrication.
Potential of hafnium nitride for the hot carrier solar cell
Simon Chung, Santosh Shrestha, Hongze Xia, et al.
The Hot Carrier solar cell is a third generation photovoltaic concept which has the potential to achieve high efficiencies, exceeding the Shockley-Queisser limit for a conventional p-n junction solar cell. The theoretical efficiencies achievable for the Hot Carrier solar cell is 65% for non-concentrated solar radiation and 85% for maximally concentrated light, very close to the limits of an infinite tandem solar cell. The approach of the Hot Carrier solar cell is to extract carriers generated before thermalisation to the bandgap edge occurs when their excess energy is lost to the environment as heat. To achieve this, the rate of carrier cooling in the absorber must be slowed down sufficiently enough to allow carriers to be collected while they are hot. This work investigates using hafnium nitride as such an absorber to restrict mechanisms of carrier cooling. Hafnium nitride’s phononic properties, where a large ‘phononic band gap’ exist can reduce the carrier cooling rate by means of a phonon bottleneck such that optical phonons cannot decay into acoustic phonons by means of the Klemens’ mechanism. Optical phonon-electron scattering can maintain a hot electron population while acoustic phonons are irrecoverable and lost as heat. The electronic and phononic properties of hafnium nitride are evaluated for their suitability to be used in a Hot Carrier solar cell absorber. Recent work on the fabrication of hafnium nitride at UNSW is presented.
A novel single dot test structure for determining specific contact resistivity
Yue Pan, Aaron M. Collins, Anthony S. Holland
The specific contact resistivity of a metal-semiconductor ohmic contact can be determined in various ways and several of these use the transmission line model approach. Concentric circular contacts have circular equipotential and using this and the transmission line model equations for such contacts, a new technique for determining specific contact resistivity is presented. An analytical technique is used to determine the error of this structure and the developed analytical equations are presented. Finite-element modeling results for Al-SiC ohmic contacts are presented to validate the analytical equations. The scaling behavior of this structure is also discussed.
Plasmonics III
Plasmonics: the convergence between optics and electronics
Surface plasmons are electrical charge oscilllations that can be excited on a metal surface by light. They provide a means by which optical energy can be converted into electrical energy and manipulated at the nanoscale. Surface plasmons can propagate as waves in waveguide devices and can exists as localised resonances in metal nanoparticles. Plasmonic circuits have been developed that mimic waveguide-based optical circuit devices, and plasmons in metal nanoparticles have been likened to excitations in electrical circuits. Although surface plasmons are electrical in nature, they preserve phase coherence with the incident optical fields that excite them. In this regard surface plasmon devices represent a convergence between optics and electronics. In this paper I review some of the work in these two fields and discuss their progress towards devices for the nanoscale control of optical signals and optical signal processing.
Vanadium dioxide thickness effects on tunable optical antennas
Stuart K. Earl, Timothy D. James, Robert E. Marvel, et al.
Vanadium Dioxide is an optically dense phase change material that has been applied to modulating the resonances of plasmonic structures resonant in the THz, infrared and optical ranges. It has been shown previously that fabrication of optical antennas on thin films of Vanadium Dioxide can result in a resonance shift of more than 10% across the phase change. This post-fabrication, dynamic tuning mechanism has the potential to significantly increase the possible applications of plasmonic devices.

Here, we show that optical antenna arrays fabricated on differing thicknesses of Vanadium Dioxide supported by a silicon substrate show a dependence of their resonant wavelengths on this thickness. Along with the geometry of the antennas in the arrays this constitutes an additional degree of freedom in the design of the tuning range of these devices, offering further potential for optimisation of this mechanism. The potential extra blue-shift provided by optimising this thickness may be used, for example, in lieu of reducing antenna dimensions to avoid increasing antenna absorption and the additional plasmonic heating that can result.
A versatile instrumentation system for MEMS-based device optical characterization
Future improvements in spectral imaging systems can be attained through the integration of MEMS-based optical transmission devices matched with pixelated arrays. Such integrated module designs will require a detailed knowledge of the MEMS device optical properties at high spatial resolution and over a wide range of operating conditions. A substantially automated low-cost optical characterization system has been developed, which enables the optical transmission of the MEMS device be measured with high spatial and spectral precision. This Optical Metrology System (OMS) can focus light on the device under test (DUT) to a spot diameter of less than 30 μm, and characterize devices at near infrared for wavelengths within the spectral band from 1.4 μm to 2.6 μm. A future upgrade to the OMS will enable measurements to be carried out across a wide range of DUT temperatures and with a spectral range from visible to long wave infrared wavelengths.
Microfludics III
Buried picolitre fluidic channels in single-crystal diamond
Michelle A. Strack, Barbara A. Fairchild, Andrew D. C. Alves, et al.
We report the generation of sub-surface nanouidic channels from single crystal diamond. To make the channels, we used a combination of ion-beam induced damage and annealing to create a buried, etchable graphitic layer in the diamond. Either laser or focussed ion-beam milling was then used to connect to that layer, and subsequent electro-chemical etching used to remove the graphitic material. The channels had dimensions 100-200 nm thick, 100 μm wide and 300 μm long, which have a total volume around 3 pL; and were around 3 μm below the diamond surface.
How to fabricate robust microfluidic systems for a dollar
Florian Lapierre, Neil R. Cameron, John Oakeshott, et al.
Since the past decade, the interest towards microfluidic devices has sensibly grown due to the wide variety of multidisciplinary applications. One branch of the microfluidic domain consists in the synthesis of various types of emulsions requested by cosmetic, food and biotechnological industries In particular, monodisperse water-in-oil microemulsion synthetised in microfluidic devices are quickly becoming the new generation of emulsions for precise bead control and high surface area. These microemulsions are generally aqueous bioreactors in the form of droplets from 500 nm to 10 μm in diameter, enclosed in an oil environment. An increasing demand for bigger emulsions has led us to investigate new techniques for fabricating fluidic devices allowing a better control over the final size of the droplets. An easy, cheap, reproducible and fast technology for generating emulsions in the range of 100s μm with high throughout (up to mL/h) is reported. Simply using pipette tips and tubing, an innovative microfluidic device was fabricated, able to synthetise water-in-oil emulsions within the range 50 – 500 _μm and double emulsions. These new emulsions are currently used for the synthesis of highly porous polymers beads from High Internal Phase Emulsion (HIPE). These beads will find high potential in 3D cell culture due to their high porosity (up to 90%) and pore size (from 5 to 30μm).
Modeling and fabrication of scale-like cantilever for cell capturing
The micro-domain provides excellent conditions for performing biological experiments on small populations of cells and has given rise to the proliferation of so-called lab-on-a-chip devices. In order to fully utilize the benefits of cell assays, means of retaining cells at defined locations over time are required. Here, the creation of scale-like cantilevers, inspired by biomimetics, on planar silicon nitride (Si3N4) film using focused ion beam machining is described. Using SEM imaging, regular tilting of the cantilever with almost no warping of the cantilever was uncovered. Finite element analysis showed that the scale-like cantilever was best at limiting stress concentration without difficulty in manufacture and having stresses more evenly distributed along the edge. It also had a major advantage in that the degree of deflection could be simply altered by changing the central angle. From a piling simulation conducted, it was found that a random delivery of simulated particles on to the scale-like obstacle should create a triangular collection. In the experimental trapping of polystyrene beads in suspension, the basic triangular piling structure was observed, but with extended tails and a fanning out around the obstacle. This was attributed to the aggregation tendency of polystyrene beads that acted on top of the piling behavior. In the experiment with bacterial cells, triangular pile up behind the cantilever was absent and the bacteria cells were able to slip inside the cantilever’s opening despite the size of the bacteria being larger than the gap. Overall, the fabricated scale-like cantilever architectures offer a viable way to trap small populations of material in suspension.
Nanoimprint lithography for microfluidics manufacturing
Gerald Kreindl, Thorsten Matthias
The history of imprint technology as lithography method for pattern replication can be traced back to 1970’s but the most significant progress has been made by the research group of S. Chou in the 1990’s. Since then, it has become a popular technique with a rapidly growing interest from both research and industrial sides and a variety of new approaches have been proposed along the mainstream scientific advances. Nanoimprint lithography (NIL) is a novel method for the fabrication of micro/nanometer scale patterns with low cost, high throughput and high resolution. Unlike traditional optical lithographic approaches, which create pattern through the use of photons or electrons to modify the chemical and physical properties of the resist, NIL relies on direct mechanical deformation of the resist and can therefore achieve resolutions beyond the limitations set by light diffraction or beam scattering that are encountered in conventional lithographic techniques. The ability to fabricate structures from the micro- to the nanoscale with high precision in a wide variety of materials is of crucial importance to the advancement of micro- and nanotechnology and the biotech- sciences as a whole and will be discussed in this paper. Nanoimprinting can not only create resist patterns, as in lithography, but can also imprint functional device structures in various polymers, which can lead to a wide range of applications in electronics, photonics, data storage, and biotechnology.
Solar IV
Plasmonic nanoparticles enhanced dye-sensitized solar cells
Qi Xu, Fang Liu, Weisi Meng, et al.
Here we present investigations on utilizing two kinds of plasmonic nanoparticles (NPs) to enhance the efficiency of dye sensitized solar cells (DSCs). The Au@PVP NPs is proposed and present the specialty of adhesiveness to dye molecules, which could help to localize additional dye molecules near the plasmonic NPs, hence increasing the optical absorption consequently the power conversion efficiency (PCE) of the DSCs by 30% from 3.3% to 4.3%. Meanwhile, an irregular Au-Ag alloy popcorn-shaped NPs (popcorn NPs) with plenty of fine structures is also proposed and realized to enhance the light absorption of DSC. A pronounced absorption enhancement in a broadband wavelength range is observed due to the excitation of localized surface plasmon at different wavelengths. The PCE is enhanced by 32% from 5.94% to 7.85%.
Ageing effects on plasmonic properties for solar cell applications
S. Pillai, Y. Yang, Y. Jiang, et al.
Metal nanoparticles are known for their unique optical properties due to surface plasmon excitations. The far field and near field effects from these metal particles have been captured to enhance efficiency of thin film solar cells by way of light trapping. Our group has extensively studied the different design parameters for a plasmon enhanced solar cell like effect of metal size/shape, location, effect of dielectric layer thickness and also the effect of plasmons on the electrical properties like passivation of cells. Whilst identifying and minimising parasitic absorption losses in these metal particles are important and is attracting lot of attention, we choose to look at a more interesting issue of ageing effects. Plasmonics at the moment promises efficiency enhancements exceeding 30% including associated losses in metals. However as is needed for solar cells, the technologies incorporated have to stand the test of time. In this work we look at the age effects on the plasmon performance by analysing our cells over time. Our preliminary results show that plasmons supported by silver metal nanoparticles can degrade by upto 10% with time. Metal nanoparticles when exposed to air can get tarnished easily causing degradation of the plasmonic properties. This will result in weakening of the scattering and reduce light trapping effects. We also look at ways of minimizing the ageing losses by overcoating. MgF2 is used as the dielectric film to overcoat metal nanoparticles preventing degradation and also to isolate MNP layer from the back surface reflector of cells. Our results show that such a rear scheme brings an additional current enhancement over interested wavelength region improving over time.
Nanomaterials IV
New efficient p-n heterojunction of BiOI/TiO2 nanotube arrays with enhanced visible-light photoelectrocatalytic activities
Jiaqin Liu, Lili Ruan, Jiajia Hu, et al.
New flake-tube structured p-n heterojunction of BiOI/TiO2 nanotube arrays (TNTAs) were successfully prepared by loading large amounts of BiOI nanoflakes onto both the outer and inner walls of well-separated TiO2 nanotubes via anodization followed by sequential chemical bath deposition (S-CBD) method. The as-prepared BiOI/TNTAs samples with different deposition cycles were characterized by X-ray diffraction, electron microscopy, UV-vis diffuse reflectance spectroscopy and nitrogen sorption. The photoelectrocatalytic (PEC) activity of the BiOI/TNTAs samples toward degradation of methyl orange (MO) solutions under visible-light irradiation were further evaluated. The visible-light PEC activity of BiOI/TNTAs samples were further confirmed by the transient photocurrent response test. In this paper, the 5-BiOI/TNTAs sample with the best PEC activity and the highest photocurrent density among all the BiOI/TNTAs samples was chosen as the typical delegates and emphatically discussed. The results from the current study revealed that TNTAs consisting of well-separated nanotubes with large tube spacings were first fabricated via increasing the water proportion in electrolyte to 10 vol. %. The synergetic effects of several factors may contribute to the remarkably enhanced PEC activities of the 5-BiOI/TNTAs sample, including a 3D connected intertube spacing system and open tube-mouth structure, strong visible-light absorption by BiOI, the formation of p-n heterojunction, larger specific surface area, and the impact of the applied external electrostatic field.
Porous CNTs/chitosan composite with lamellar structure prepared by ice-templating
Tianhao Wu, Jia Yan, Minjing Liu
Chitosan possesses beneficial properties such as its biodegradability, biocompatibility, and adsorption of metallic ions, which make it attractive in various applications. In addition, besides excellent mechanical and electrical properties, carbon nanotubes have been reported to be biocompatible platforms for neuronal growth and differentiation. In this work, porous carbon nanotubes/chitosan (CNTs/CHI) composites are prepared by unidirectional freezing CNTs dispersion in chitosan aqueous solution and subsequent freeze drying, which is named as ice-templating. Two types of macroscopic shapes with high and low aspect ratio are produced by immersion freezing and one-side contact freezing respectively. The SEM characterization indicates that the produced CNTs/CHI composites are composed of a three dimensional network with lamellar structure and macropores in micron scale, and the products by two freezing styles have different micro-structural characters. The produced CNTs/CHI composite has a very low density and self-standing ability, which makes it having very good permeability and processability. It is anticipated that the CNTs/CHI composites have various applications such as conductive network in polymer, biological carrier, catalyst supports, adsorbents, and permeable membranes.
Bio IV
Integrated microdroplet-based system for enzyme synthesis and sampling
Florian Lapierre, Michel Best, Robert Stewart, et al.
Microdroplet-based microfluidic devices are emerging as powerful tools for a wide range of biochemical screenings and analyses. Monodispersed aqueous microdroplets from picoliters to nanoliters in volume are generated inside microfluidic channels within an immiscible oil phase. This results in the formation of emulsions which can contain various reagents for chemical reactions and can be considered as discrete bioreactors. In this paper an integrated microfluidic platform for the synthesis, screening and sorting of libraries of an organophosphate degrading enzyme is presented. The variants of the selected enzyme are synthesized from a DNA source using in-vitro transcription and translation method. The synthesis occurs inside water-in-oil emulsion droplets, acting as bioreactors. Through a fluorescence based detection system, only the most efficient enzymes are selected. All the necessary steps from the enzyme synthesis to selection of the best genes (producing the highest enzyme activity) are thus integrated inside a single and unique device. In the second part of the paper, an innovative design of the microfluidic platform is presented, integrating an electronic prototyping board for ensuring the communication between the various components of the platform (camera, syringe pumps and high voltage power supply), resulting in a future handheld, user-friendly, fully automated device for enzyme synthesis, screening and selection. An overview on the capabilities as well as future perspectives of this new microfluidic platform is provided.
A microfluidic device for studying cell signaling with multiple inputs and adjustable amplitudes and frequencies
Zubaidah Ningsih, James W. M. Chon, Andrew H. A. Clayton
Cell function is largely controlled by an intricate web of macromolecular interactions called signaling networks. It is known that the type and the intensity (concentration) of stimulus affect cell behavior. However, the temporal aspect of the stimulus is not yet fully understood. Moreover, the process of distinguishing between two stimuli by a cell is still not clear. A microfluidic device enables the delivery of a precise and exact stimulus to the cell due to the laminar flow established inside its micro-channel. The slow stream delivers a constant stimulus which is adjustable according to the experiment set up. Moreover, with controllable inputs, microfluidic facilitates the stimuli delivery according to a certain pattern with adjustable amplitude, frequency and phase. Several designs of PDMS microfluidic device has been produced in this project via photolithography and soft lithography processes. To characterize the microfluidic performance, two experiments has been conducted. First, by comparing the fluorescence intensity and the lifetime of fluorescein in the present of KI, mixing extent between two inputs was observed using Frequency Lifetime Imaging Microscopy (FLIM). Furthermore, the input-output relationship of fluorescein concentration delivered was also drawn to characterize the amplitude, frequency and phase of the inputs. Second experiment involved the cell culturing inside microfluidic. Using NG108-15 cells, proliferation and differentiation were observed based on the cell number and cell physiological changes. Our results demonstrate that hurdle design gives 86% mixing of fluorescein and buffer. Relationship between inputoutput fluorescein concentrations delivered has also been demonstrated and cells were successfully cultured inside the microfluidic.
Micro pore arrays in free standing cyclic olefin copolymer membranes: fabrication and surface functionalization strategies for in-vitro barrier tissue models
M. Gel, S. Kandasamy, K. Cartledge, et al.
In recent years there has been growing interest in micro engineered in-vitro models of tissues and organs. These models are designed to mimic the in-vivo like physiological conditions with a goal to study human physiology in an organ-specific context or to develop in-vitro disease models. One of the challenges in the development of these models is the formation of barrier tissues in which the permeability is controlled locally by the tissues cultured at the interface. In-vitro models of barrier tissues are typically created by generating a monolayer of cells grown on thin porous membranes. This paper reports a robust preparation method for free standing porous cyclic olefin copolymer (COC) membranes. We also demonstrate that gelatin coated membranes facilitate formation of highly confluent monolayer of HUVECs. Membranes with thickness in the range of 2-3 um incorporating micro pores with diameter approximately 20 um were fabricated and integrated with microfluidic channels. The performance of the device was demonstrated with a model system mimicking the endothelial barrier in bone marrow sinusoids.
Photonics IV
Proposal of a Si based device for multiplexing conversion between PDM and MDM
Mengyuan Ye, Yu Yu, Lei Xiang, et al.
A novel concept for a compact SOI device used to achieve the conversions between the polarization division multiplexing (PDM) and the mode division multiplexing signals (MDM) is proposed and simulated by utilizing a structure combining a 2D grating coupler and a two-mode multiplexer. The detailed design of the proposed device is given and the simulations show the good performance of the device. The proposed device can be useful for accommodating the future fiber optic communication networks which utilizing multiple multiplexing techniques.
Chiral elements and dual systems: towards the design of an omnidirectional optical active media
Xavier Vidal, Xavier Zambrana-Puyalto, Alex F. Barbara, et al.
We will show how to extract information from the Mie coefficients to properly design dual systems combined with chiral elements for having optically active structures. Such optically active elements will scatter the light omnidirectionally, where the amount of rotation of light is fixed in any given direction independently of the incident polarization. The key elements are the preservation of helicity by equaling the electric and magnetic responses from the material, and by the proper manipulation of the angular momentum.
Steady state design of photonic transistor to achieve a switching gain>=3 dB
V. Krishnamurthy, Yijing Chen, S. T. Ho
A recently proposed two-staged photonic transistor that provides switching gain is based on the directional coupler with an active arm and a passive arm in each stage. The manipulation of optical interference through optically-controlled gain caused the switching. In the first stage, a long wavelength input signal pulse depletes carriers to change absorption and switch a short wavelength beam into the second stage. In the second stage, the switched short wavelength beam fills the conduction band with carriers to increase the gain seen by another long wavelength pump beam to switch it as the output signal. Through a suitable design of intensity and wavelength of the interacting beams and the length of each stage, photonic transistor exhibits switching gain and hence can drive multiple stages (high fan-out and cascadability). The smaller the detuning of wavelength between the interacting optical fields or shorter the photonic transistor length, smaller is the cumulative change in linear absorption/gain, manifesting in a smaller switching gain. Since the short wavelength beam fills the conduction band with carriers, its intensity depends on the ground state absorption of the medium, α0. And, since the long wavelength beam depletes carriers filled by the short wavelength beam, its wavelength depends on the gain of the pumped medium, g0. In this paper, we show that the operational intensities of photonic transistor must be such that |α0L1|>27 and g0L2>3.2 to achieve a gain>3dB, where L1 and L2 are the length of 1st and 2nd stages respectively.
Materials II
Non-intrusive tunable resonant microwave cavity for optical detected magnetic resonance of NV centres in nanodiamonds
Jean-Michel Le Floch, Carlo Bradac, Thomas Volz, et al.
Optically detected magnetic resonance (ODMR) in nanodiamond nitrogen-vacancy (NV) centres is usually achieved by applying a microwave field delivered by micron-size wires, strips or antennas directly positioned in very close proximity (~ μm) of the nanodiamond crystals. The microwave field couples evanescently with the ground state spin transition of the NV centre (2.87 GHz at zero magnetic field), which results in a reduction of the centre photoluminescence. We propose an alternative approach based on the construction of a dielectric resonator. We show that such a resonator allows for the efficient detection of NV spins in nanodiamonds without the constraints associated to the laborious positioning of the microwave antenna next to the nanodiamonds, providing therefore improved flexibility. The resonator is based on a tunable Transverse Electric Mode in a dielectric-loaded cavity, and we demonstrate that the resonator can detect single NV centre spins in nanodiamonds using less microwave power than alternative techniques in a non-intrusive manner. This method can achieve higher precision measurement of ODMR of paramagnetic defects spin transition in the micro to millimetre-wave frequency domain. Our approach would permit the tracking of NV centres in biological solutions rather than simply on the surface, which is desirable in light of the recently proposed applications of using nanodiamonds containing NV centres for spin labelling in biological systems with single spin and single particle resolution.
Fabrication III
A fabrication method of out-of-plane stretchable and flexible electrodes based on PDMS
We developed stretchable and flexible out-of-plane electrodes based on PDMS substrate using general MEMS fabrication processes. The electrodes were designed to be used for devices that require large elongation without electrical disconnection. Thus, the stretchable electrode was designed to have serpentine metal line suspended above the substrate along its entire length. To fabricate the out-of-plane structure, the metal pattern of the electrode was created on a parylene layer that was suspended above the PDMS substrate by using sacrificial photoresist layer. The metal line was covered by a second parylene layer, thereby encapsulated and electrically insulated. In serpentine electrodes, the parylene layer was attached with PDMS substrate through parylene posts located nearby the metal line, which restrained lateral movements of the metal line. The stretch test, bending test, and twist test were performed using our customdesigned test modules to characterize the stretchability and flexibility of the fabricated electrodes. With up to 32 % strain, with various bending radii, and up to 360° twist angle, stable electrical connection was demonstrated. From these results, the proposed out-of-plane electrodes would be useful in stretchable and flexible applications such as wearable electronics and biomedical devices.
Photonics V
Chiral photonic crystals with four-fold symmetry: band structure and S-parameters of eight-fold intergrown Gyroid nets
Matthias Saba, Mark D. Turner, Min Gu, et al.
The Single Gyroid, or srs, nanostructure has attracted interest as a circular-polarisation sensitive photonic material. We develop a group theoretical and scattering matrix method, applicable to any photonic crystal with symmetry I432, to demonstrate the remarkable chiral-optical properties of a generalised structure called 8-srs, obtained by intergrowth of eight equal-handed srs nets. Exploiting the presence of four-fold rotations, Bloch modes corresponding to the irreducible representations E_ and E+ are identified as the sole and non-interacting transmission channels for right- and left-circularly polarised light, respectively. For plane waves incident on a finite slab of the 8-srs, the reflection rates for both circular polarisations are identical for all frequencies and transmission rates are identical up to a critical frequency below which scattering in the far field is restricted to zero grating order. Simulations show the optical activity of the lossless dielectric 8-srs to be large, comparable to metallic metamaterials, demonstrating its potential as a nanofabricated photonic material.
Nanomaterials V
Electrodeposition and characterization of Sb-doped ZnO nanostructures
Jinkun Liang, Hailin Su, Yucheng Wu, et al.
Large scale Sb-doped ZnO nanorod arrays were grown utilizing electrochemical solution method with suitable combination of Zn(NO3)2, HMT and SbCl3 precursors. The influences of the pH value and the substrate on the morphology and the crystallization of Sb-doped ZnO nanorods were investigated in detail. The formed Sb-doped ZnO nanorods were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Characteristics of luminescence and crystal qualities were represented by the room temperature photoluminescence spectroscopy. It was found that the pH value had a great effect on the luminescent intensity of the ultraviolet peak and the defect-related luminescence peak. The Sb-ZnO nanorods with a hexagonal wurtzite structures fabricated under the pH value of 5 showed an intense ultraviolet emission and a weak visible emission, demonstrating the good crystal quality of the nanorods. For the substrates of flexible conductive woven nickel-copper fibers, ITO conductive glass and commercial AZO conductive glass, well-crystallized Sb-doped ZnO nanorods can be all achieved. But the crystallographic orientation of nanorods strongly relied on the substrate type.
Poster Session
Fabrication of Fresnel zone plate lens in fused silica glass using femtosecond laser lithography technology
Ik-Bu Sohn, Md. Shamim Ahsan, Young-Chul Noh, et al.
This paper demonstrates mask-less formation of Fresnel zone plate lens on the surface of a fused silica glass substrate using femtosecond laser lithography technology. The lens consists of a series of concentric rings, which has been fabricated on the glass surface by femtosecond laser writing followed by chemical etching and stripping. We also pattern Fresnel zone plate on fused silica glass surface using direct femtosecond laser writing technique. The both Fresnel zone plate lenses have a focal length of 50 mm. Femtosecond laser lithography technique offers smooth patterning of materials compared to traditional femtosecond laser writing. Consequently, femtosecond laser lithography induced Fresnel zone plate lens yields considerably high diffraction efficiency. Using these Fresnel zone plate lenses, we are able to observe the micro-letters, micro-machined on aluminum coated poly-methylmethacrylate (PMMA) surface indicating excellent focusing and imaging capability of the Fresnel zone plate lenses. The proposed mask-less technology is simple compared to other lithography techniques, which shows great potential for small-scale manufacturing of similar kinds of optical devices.
On-chip optical nano-scale displacement sensor
In this paper, a high-speed on-chip optical displacement sensing and self-actuating mechanisms have been designed and simulated for an AFM application. This mechanism can allow significantly smaller cantilever beams to be made with higher sensitivity and wide bandwidth for parallel imaging through array of cantilevers. This arrangement consists of a Si-waveguide in which a nano-scale free space gap is fabricated in the direction of light propagation.One portion of the Si-waveguide is a suspended cantilever with a thin film PZT formed on it for actuation. The optical power coupling loss between the waveguides is used to measure the cantilever displacement. The simulation results show that the device can achieve a 6.25MHz resonant frequency in air, 0.195N/m spring constant and less than 0.1nm sensitivity. This approach can overcome the conventional cantilever size limit of an AFM to achieve high bandwidth with low spring constant.
Immobilization of lipase and keratinase on functionalized SBA-15 nanostructured materials
Hy G. Le, Tuan A. Vu, Hoa T. K. Tran, et al.
SBA-15 nanostructured materials were synthesized via hydrothermal treatment and were functionalized with 3- aminopropyltriethoxysilane (APTES). The obtained samples were characterized by different techniques such as XRD, BET, TEM, IR and DTA. After functionalization, it showed that these nanostrucrured materials still maintained the hexagonal pore structure of the parent SBA-15. The model enzyms chosen in this study were lipase and keratinase. Lipase was a biocatalyst for hydrolyzation of long chain triglycerides or methyl esters of long chain alcohols and fatty acids; keratinase is a proteolytic enzyme that catalyzes the cleavage of keratin. The functionalized SBA-15 materials were used to immobilize lipase and keratinase, exhibiting higher activity than that of the unfunctionalized pure silica SBA-15 ones. This might be due to the enhancing of surface hydrophobicity upon functionalization. The surface functionalization of the nanostructured silicas with organic groups can favor the interaction between enzyme and the supports and consequently increasing the operational stability of the immobilized enzymes. The loading of lipase on functionalized SBA-15 materials was higher than that of keratinase. This might be rationalized by the difference in size of enzyms.
Additive manufacturing of lab-on-a-chip devices: promises and challenges
Feng Zhu, Niall P. Macdonald, Jonathan M. Cooper, et al.
This work describes a preliminary investigation of commercially available 3D printing technologies for rapid prototyping and low volume fabrication of Lab-on-a-Chip devices. The main motivation of the work was to use off-the-shelf 3D printing methods in order to rapidly and inexpensively build microfluidic devices with complex geometric features and reduce the need to use clear room environment and conventional microfabrication techniques. Both multi-jet modelling (MJM) and stereolithography (SLA) processes were explored. MJM printed devices were fabricated using a HD3500+ (3D Systems) high-definition printer using a thermo-polymer VisiJet Crystal (3D Systems) substratum that allows for a z-axis resolution of 16 μm and 25 μm x-y accuracy. SLA printed devices were produced using a Viper Pro (3D Systems) stereolithography system using Watershed 11122XC (DSM Somos) and Dreve Fototec 7150 Clear (Dreve Otoplastik GmbH) resins which allow for a z-axis resolution of 50 μm and 25 μm x-y accuracy. Fabrication results compared favourably with other forms of rapid prototyping such as laser cut PMMA devices and PDMS moulded microfluidic devices of the same design. Both processes allowed for fabrication of monolithic, optically transparent devices with features in the 100 μm range requiring minimal post-processing. Optical polymer qualities following different post-processing methods were also tested in both brightfield and fluorescence imaging of transgenic zebrafish embryos. Finally, we show that only ethanol-treated Dreve Fototec 7150 Clear resign proved to be non-toxic to human cell lines and fish embryos in fish toxicity assays (FET) requiring further investigation of 3D printing materials.
A high-throughput lab-on-a-chip interface for zebrafish embryo tests in drug discovery and ecotoxicology
Feng Zhu, Jin Akagi, Chris J. Hall, et al.
Drug discovery screenings performed on zebrafish embryos mirror with a high level of accuracy. The tests usually performed on mammalian animal models, and the fish embryo toxicity assay (FET) is one of the most promising alternative approaches to acute ecotoxicity testing with adult fish. Notwithstanding this, conventional methods utilising 96-well microtiter plates and manual dispensing of fish embryos are very time-consuming. They rely on laborious and iterative manual pipetting that is a main source of analytical errors and low throughput. In this work, we present development of a miniaturised and high-throughput Lab-on-a-Chip (LOC) platform for automation of FET assays. The 3D high-density LOC array was fabricated in poly-methyl methacrylate (PMMA) transparent thermoplastic using infrared laser micromachining while the off-chip interfaces were fabricated using additive manufacturing processes (FDM and SLA). The system’s design facilitates rapid loading and immobilization of a large number of embryos in predefined clusters of traps during continuous microperfusion of drugs/toxins. It has been conceptually designed to seamlessly interface with both upright and inverted fluorescent imaging systems and also to directly interface with conventional microtiter plate readers that accept 96-well plates. We also present proof-of-concept interfacing with a high-speed imaging cytometer Plate RUNNER HD® capable of multispectral image acquisition with resolution of up to 8192 x 8192 pixels and depth of field of about 40 μm. Furthermore, we developed a miniaturized and self-contained analytical device interfaced with a miniaturized USB microscope. This system modification is capable of performing rapid imaging of multiple embryos at a low resolution for drug toxicity analysis.
Immobilization of zebrafish larvae on a chip-based device for environmental scanning electron microscopy (ESEM) imaging
Jin Akagi, Chris J. Hall, Kathryn E. Crosier, et al.
Small vertebrate model organisms have recently gained popularity as attractive experimental models that enhance our understanding of human tissue and organ development. Laser microsurgery on zebrafish larvae combined with Scanning Electron Microscopy (SEM) imaging can in particular provide accelerated insights into the tissue regeneration phenomena. Conventional SEM exposes, however, specimens to high vacuum environments, and often requires laborintensive and time-consuming pretreatments and manual positioning. Moreover, there are virtually no technologies available that can quickly immobilize the zebrafish larvae for high definition SEM imaging. This work describes the proof-of-concept design and validation of a microfluidic chip-based system for immobilizing zebrafish larvae and it’s interfacing with Environmental Scanning Electron Microscope (ESEM) imaging. The Lab-on-a-Chip (LOC) device was fabricated using a high-speed infrared laser micromachining and consists of a reservoir with multiple semispherical microwells, which hold the yolk of zebrafish larvae, and drain channels that allow removing excess of medium during SEM imaging. Paper filter is used to actuate the chip and immobilization of the larvae by gentle suction that occurs during water drainage. The trapping region allows multiple specimens to be positioned on the chip. The device is then inserted directly inside the ESEM and imaged in a near 100% humidity atmosphere. This facilitates ESEM imaging of untreated biological samples.
Microfluidic EmbryoSort technology: towards in flow analysis, sorting and dispensing of individual vertebrate embryos
Nurul Mohd Fuad, Donald Wlodkowic
The demand to reduce the numbers of laboratory animals has facilitated the emergence of surrogate models such as tests performed on zebrafish (Danio rerio) or African clawed frog’s (Xenopus levis) eggs, embryos and larvae. Those two model organisms are becoming increasingly popular replacements to current adult animal testing in toxicology, ecotoxicology and also in drug discovery. Zebrafish eggs and embryos are particularly attractive for toxicological analysis due their size (diameter 1.6 mm), optical transparency, large numbers generated per fish and very straightforward husbandry. The current bottleneck in using zebrafish embryos for screening purposes is, however, a tedious manual evaluation to confirm the fertilization status and subsequent dispensing of single developing embryos to multitier plates to perform toxicity analysis. Manual procedures associated with sorting hundreds of embryos are very monotonous and as such prone to significant analytical errors due to operator’s fatigue. In this work, we present a proofof- concept design of a continuous flow embryo sorter capable of analyzing, sorting and dispensing objects ranging in size from 1.5 – 2.5 mm. The prototypes were fabricated in polymethyl methacrylate (PMMA) transparent thermoplastic using infrared laser micromachining. The application of additive manufacturing processes to prototype Lab-on-a-Chip sorters using both fused deposition manufacturing (FDM) and stereolithography (SLA) were also explored. The operation of the device was based on a revolving receptacle capable of receiving, holding and positioning single fish embryos for both interrogation and subsequent sorting. The actuation of the revolving receptacle was performed using a DC motor and/or microservo motor. The system was designed to separate between fertilized (LIVE) and non-fertilized (DEAD) eggs, based on optical transparency using infrared (IR) emitters and receivers.
Eye trackers in an oculary clinical setting
Mizhanim M. Shahimin, Mukhzeer M. Shahimin
Infrared eye tracker has been demonstrated to provide a more objective and quantitative results of the cover test measurement in eye care practices. This paper reviews the application of eye trackers in oculary clinical setting. It highlights the different types of eye movement recording system (EMRS) available, the advantages and disadvantages of each and their use in a clinical setting. This paper also discusses the parameters that can be derived from the EMRS and the significance of the parameters in a clinical interpretation. Using an eye tracker would make available to the clinician a simple system for making quantitative measurements when performing the cover test in an eye examination.
Performance characteristics of valveless and cantilever-valve micropump
A. F. M. Shukur, N. Sabani, B. N. Taib, et al.
This paper presents comparison between two classes of micropump which are valveless micropump and cantilever-valve micropump. These micropumps consist of basic components which are diaphragm, pumping chamber, actuation mechanism, inlet and outlet. Piezoelectric actuation is carried out by applying pressure on the micropump diaphragm to produce deflection. The micropumps studied in this paper had been designed with specific diaphragm thickness and diameter; while varying the materials, pressure applied and liquid types used. The outer dimension for both micropumps is 4mm × 4mm × 0.5mm with diameter and thickness of the diaphragm are 3.8mm and 20μm respectively. Valveless micropump was shown in this paper to have better performance in mechanical and fluid analysis in terms of maximum deflection and maximum flow rate at actuation pressure 30kPa vis-à-vis cantilever-valve micropump. Valveless micropump was shown in this study to have maximum diaphragm deflection of 183.06μm and maximum flow rate with 191.635μL/s at actuation pressure 30kPa using silicon dioxide as material.
The application and quantitative testing of 150 million pixel CMOS image sensor
Xueyi Gong, Fansheng Cheng, Sijie Huang, et al.
With the requirements of high time resolution, high spatial and high spectral resolution development in geostationary orbit, photodetector pixel size has gradually become the bottleneck of the space exploration technology. Shanghai Institute of Technical Physics of Chinese Academy of Science has made a new breakthrough in CMOS image sensor area. The scale of its new CMOS image sensor achieves 2.5K×2.5K, and then use 24 detectors to achieve a detector whose scale is 150 million. The detector has been successfully imaging on the ground. In the application process, presents a systematic test and measurement methods to deal with the time noise, dark current, fixed pattern noise, MTF and other parameters of the detector. The test results are below. The MTF of the detector is 0.565 which is measured at 57.21/mm Nyquist frequency. The number of saturated electrons reaches 8.9×104. The total number of transient noise electrons is smaller than 16. The signal to noise ratio is 58.02dB. Through comprehensive analysis and measurement, it shows that the overall performance of the 2.5K×2.5K detector among the same types of products is in the leading position currently.
Optimization of physical parameters of 'injected' metal electrodes for capacitively coupled contactless conductivity detection on poly(dimethylsiloxane) microchips
Leigh D. Thredgold, Dmitriy A. Khodakov, Amanda V. Ellis, et al.
Capacitively coupled contactless conductivity detection (C4D) and its integration with Lab-on-a-Chip (LOC) systems has been well studied. However, most reported methods require multi-step electrode patterning/fabrication processes which in turn leads to difficulty in consistently aligning detection electrodes. These limitations have the potential to compromise analytical performance of the electrodes and increase the time and cost of device production. We have previously demonstrated a simplified approach for C4D electrode integration with poly(dimethylsiloxane) electrophoresis LOC devices by utilizing ‘injected’ gallium electrodes.1 The developed fabrication process is fast, highly reproducible, and eliminates difficulties with electrode alignment. Using this approach C4D can be readily achieved in any microchip by simply adding extra ‘electrode’ channels to the microchip design. This design flexibility allows for straightforward optimization of electrode parameters. Here, we present the optimization of physical electrode parameters including orientation, length and distance from separation channel. The suitability of the optimized system for on-chip C4D detection was demonstrated through the excellent intra- and inter-day repeatability (< 4 %RSD) of electrophoretically separated lithium, sodium and potassium ions.
Effect of mesh element type of Finite Element Model (FEM) on unimorph cantilever vibration
This paper discusses mesh refinement methods used to perform Finite Element Analysis (FEA) for vibration based MEMS Energy Harvester. The three types of meshing elements, 1) Linear Hexahedral, 2) Parabolic Hexahedral and 3) Parabolic Tetrahedral, were used in this study. The meshing methods are used to ensure accurate simulation result particularly in stress, and strain analysis obtained, since they are determined by the displacement of each node in the physical structure. The study of the accuracy of an mesh analysis is also known as mesh convergence study which element aspect ratios must be refined consistently. In this paper the dimensions of each elements were also varied in order to investigate the significant of this methods in achieving better ratios of simulation to theoretical results.
Metal-oxide-semiconductor field-effect transistors operated by surface plasmon polaritons
Takuma Aihara, Ayumi Takeda, Masashi Fukuhara, et al.
The operation of a metal-oxide-semiconductor field-effect transistor (MOSFET) by a surface plasmon (SP) signal was demonstrated. The SP detector, composed of a gold/silicon Schottky diode with a nano-slit grating, was monolithically integrated with the MOSFETs on a silicon substrate. SP generation by the nano-slit gating (slit width of 100 nm, slit pitch of 440 nm, and slit depth of 300 nm) was confirmed by analytical calculations based on the finite-difference timedomain method. The SP detector operated at a photon energy (0.80 eV) that was below the bandgap energy of silicon (1.1 eV), with responsivity of 24 nA/mW and a dark current of 1.7 nA under reverse bias of 5.0 V. The photocurrent generated by the SP detector controlled the drain current of a monolithically integrated MOSFET.
Sensitivity improvement of Schottky-type plasmonic detector
Ayumi Takeda, Takuma Aihara, Masashi Fukuhara, et al.
A surface plasmon polariton (SPP) is composed of collective electron oscillations that confine optical energies in nanoscale beyond the diffraction limit. This advantage of SPPs has promoted the development of high-density optoelectronic integrated circuits (OEICs) using SPPs. Schottky-type plasmonic detectors have attracted particular attention, because these devices show sensitivity in the telecommunications wavelength range and can be integrated into Si-based electronic circuits with a simple fabrication process. We have developed an Au/Si Schottky-type plasmonic detector with nano slits that excites SPPs at the Au/Si interface. In this report, we demonstrate a novel nano-slit arrangement that provides a sensitivity improvement for the detector. Using the finite-difference time-domain method, we have shown that the highest electric field intensity in the SPP mode on the Au/Si interface is generated by positioning slits with twice the pitch of the SPP wavelength at the Au/Si interface. Using this slit pitch, a weaker SPP mode intensity on the air/Au interface and a stronger SPP mode intensity at the Au/Si interface have also been confirmed. Nano slits with different slit pitches were formed in the Au film of the detector, and the slit pitch dependence of the photocurrent was measured. The experimental results showed similar tendencies to the simulation results. This novel nano-slit arrangement can provide an efficient plasmonic detector for future high-speed data processing applications.
A method for evaporating silicon to form low dimensional Si lattice structures
David C. Ng, Kumar Ganesan, Alastair Stacey, et al.
Physical deposition by evaporation is a convenient and cost effective method for generating thin layers of material. In this work, we utilise an electron-beam evaporation system retrofitted with a rotating shutter to control and reduce the deposition rate of materials. Under normal conditions, the evaporator is able to achieve a typical deposition rate of 1 A/s. In order to reduce the deposition rate, a rotating shutter was designed and retrofitted to the evaporator. The rotating shutter consists of a metal plate with a slit opening of 6° and 36°. When rotated during evaporation, a reduction in deposition rate of 1/60 and 1/10 onto a sample is expected. We can control the deposition to achieve a rate of 1 A/min. By using this modified system, we deposited Si and SiO2 onto Si substrates. In situ deposition is monitored using a quartz thickness monitor. After evaporation, film thickness is measured using AFM and verified with spectroscopic ellipsometer measurement. Using this method, we are able to reach a deposited film thickness of 3 nm. This work is expected to contribute significantly towards the fabrication of low dimensional silicon devices.
Catalytic pyrolysis of biomass by novel nanostructured catalysts
Phuong T. Dang, Hy G. Le, Giang T. T. Pham, et al.
Nanostructured catalysts were successfully prepared by acidification of diatomites and the regeneration of used FCC catalysts. The obtained samples were characterized by IR, XRD, SEM, EDX, MAS-NMR (27Al and 29Si), NH3-TPD and tested in catalytic pyrolysis of biomass (rice straw). The results showed that the similar bio-oil yield of 41,4% can be obtained by pyrolysis in presence of catalysts at 450°C as compared to that of the pyrolysis without catalyst at 550°C. The bio-oil yield reached a maximum of 42,55 % at the pyrolysis temperature of 500°C with catalytic content of 20%. Moreover, by catalytic pyrolysis, bio-oil quality was better as reflected in higher ratio of H/C, lower ratio of O/C. This clearly indicated high application potential of these new nanostructured catalysts in the production of bio-oil with low oxygenated compounds.
High-speed camera observation of multi-component droplet coagulation in an ultrasonic standing wave field
Marina Reißenweber, Sandro Krempel, Gerhard Lindner
With an acoustic levitator small particles can be aggregated near the nodes of a standing pressure field. Furthermore it is possible to atomize liquids on a vibrating surface. We used a combination of both mechanisms and atomized several liquids simultaneously, consecutively and emulsified in the ultrasonic field. Using a high-speed camera we observed the coagulation of the spray droplets into single large levitated droplets resolved in space and time. In case of subsequent atomization of two components the spray droplets of the second component were deposited on the surface of the previously coagulated droplet of the first component without mixing.
Fabrication and replication of micro-optical structures for growth of GaN-based light emitting diodes
G. Gervinskas, G. Seniutinas, A. Vijayakumar, et al.
GaN light emitting diodes (LEDs) on sapphire substrates can be improved by micro-patterning substrate to perform epitaxial over-growth which drastically reduces defects' density in the light emitting region. We patterned Al2O3 with focused ion beam and show a successful overgrowth of GaN. The exact shape of pattern milled into Al2O3 was replicated into a 0.4-mm-thick shim of Ni by electroplating. The surface roughness of Ni was ~5:5 ±2 nm and is applicable for the most demanding replication of nano-rough surfaces. This technique can be used to replicate at micro-optical elements Fresnel-axicons defined by electron beam lithography made on sub-1 mm areas without stitching errors (Raith EBL). Shimming of macro-optical elements such as car back- reflectors is also demonstrated. Ni-shimming opens possibility to make replicas of nano-textured small and large area patterns and use them for thermal embossing and molding of optically-functionalized micro-fluidic chips and macro-optical elements.
The NUC and blind pixel eliminating in the DTDI application
Xiaofeng Su, FanSheng Chen, Sheng Da Pan, et al.
AS infrared CMOS Digital TDI (Time Delay and integrate) has a simple structure, excellent performance and flexible operation, it has been used in more and more applications. Because of the limitation of the Production process level, the plane array of the infrared detector has a large NU (non-uniformity) and a certain blind pixel rate. Both of the two will raise the noise and lead to the TDI works not very well. In this paper, for the impact of the system performance, the most important elements are analyzed, which are the NU of the optical system, the NU of the Plane array and the blind pixel in the Plane array. Here a reasonable algorithm which considers the background removal and the linear response model of the infrared detector is used to do the NUC (Non-uniformity correction) process, when the infrared detector array is used as a Digital TDI. In order to eliminate the impact of the blind pixel, the concept of surplus pixel method is introduced in, through the method, the SNR (signal to noise ratio) can be improved and the spatial and temporal resolution will not be changed. Finally we use a MWIR (Medium Ware Infrared) detector to do the experiment and the result proves the effectiveness of the method.
A waveguide based microfluidic application
Nooshin S. Taheri, Peggy Chan, James R. Friend, et al.
Microfluidics is based on the performance of fluids in a microenvironment. As the microfluidics research advances in the cellular behaviour, the need for improved micro devices grows. This work introduces the design and fabrication of a micro ridge waveguide to be employed in fluids manipulations. Then it investigates the characteristics of the device in order to control the movement of the fluids on top of the ridge of the waveguide. The elastic vibration is excited along the ridge of the guide with the use of thickness poled lead zirconate titanate (PZT) elements attached to both sides of the waveguide. To excite anti-symmetric or flexural mode in the ridge of the guide, the propagation velocity has been kept significantly below the Rayleigh wave velocity. The velocity reduction of 15% is achieved with the high aspect ratio ridge (H/W =3) design. A three dimensional model of the micro waveguide has also been developed to determine the vibration characteristics; the natural frequency and the considered mode of the micro waveguide through finite element analysis using ANSYS. The travelling wave along the ridge of the guide is able to transmit strong vibration to the fluid atop of the substrate. The results represents a promising approach, through recasting the waveguide structure to be suitable in fluids and particle in fluids manipulations in one dimensional environment with the strong confined energy, at smaller scale with higher vibration displacement.
Long-wavelength infrared Fabry-Perot etalon for multi-spectral thermal imaging
A miniature Fabry-Perot etalon was designed and fabricated to provide spectral filtering capability at the resonance wavelength of 10 μm. A high transmission peak of 85% and a relatively broad bandwidth of 500 nm are expected based on optical modeling. Optimal deposition conditions for process durable thin film materials were developed and optical constants of these materials were characterized. Fabrication of devices was accomplished using standard surface micromachining technique. Released mirrors exhibited a deflection of 400 nm over a length of 150 μm.
Targeted sacrificial layer etching for MEMS release using microfluidic channels
A microfluidics based targeted etchant delivery and masking approach to wet etching has been used to control the etch progression of a MEMS sacrificial layer during the release of silicon nitride (SiNx) microbeams. A reusable 3-input open-channel polydimethylsiloxane (PDMS) microfluidic cassette was used to form a dynamically controllable fluid etch mask to control the location of the etchant during the wet release process. In contrast conventional release techniques which use solid masking and homogeneous etching environments, microfluidic devices can utilise laminar flows to generate heterogeneous etching conditions which can be controlled in real-time by altering the composition and flow rates of the fluids passing through specific inlets. The fluid nature of the heterogeneous flow can be used to target etch specific areas of sacrificial material or conversely, dynamically mask specific areas both above and below suspend structures. As a result of this control, structures with anchor geometries not achievable using conventional release techniques were created. Not only does this method require small volumes of etchant fluid, it is also suitable for use on samples which may be sensitive to the chemical and/or physical rigors of photolithographic patterning, such as porous silicon. Microfluidic based release etching, using dynamically controlled fluid masks, provides a valuable addition to the suite of microchannel based fabrication techniques.
Dark-field microspectroscopic analysis of gold nanorods in spiral Ganglion neurons
J. Yong, W. G. A. Brown, K. Needham, et al.
Heterogeneous samples of spiral ganglion neuron primary cells were incubated with gold nanorods in order to investigate the photothermal processes induced by exposure to 780 nm laser light. Dark-field microspectroscopy was used to analyze the distribution and spectrum of nanorods in the neurons. The scattering data showed a typical gold nanorod spectrum, while a shift in the peak position suggested changes in the refractive index of the nanorod environment. The relationship between gold nanorods distribution and local temperature has also been examined with an open pipette microelectrode placed in the surrounding bath of the neurons. These temperature measurements confirm that the gold nanorods provide efficient localized heating under 780 nm laser exposure.
Nanocrystallic thin films statistical structural analysis by the automatic image processing
Maciek Wielgus, Zofia Sunderland, Daniel Koguciuk, et al.
We demonstrate the powerful new algorithm for automatic analysis of the electron diffraction patterns in the microscopic images. The method can be outlined as follows: (1) filtration of the image in the Fourier domain (2) normalization with the bidimensional Hilbert transform, so-called vortex transform (3) local diffraction pattern frequency estimation by the finite difference operator (4) morphological filtration for the elements segmentation (5) construction of the sample features statistics. With sufficient quality maintained and vastly reduced time necessary for the computations, the method is superior to previously considered wavelet-based approach for the automatic analysis of large data sets.
Formation of cylindrical micro-lens array in fused silica glass using laser irradiations
Hun-Kook Choi, Md. Shamim Ahsan, Dongyoon Yoo, et al.
In this article, we report the development of plano-convex cylindrical micro-lens array on the surface of fused silica glass using laser processing technology. Initially, femtosecond laser pulses are irradiated on the target fused silica glass substrate to pattern periodic micro-grooves. Afterwards, laser beam from CO2 laser source is applied several times on the previously micro-patterned fused silica glass surface, the purpose of which is to polish the micro-patterned glass surface. As a consequence, periodic plano-convex cylindrical micro-lens array is evolved on the glass surface. The micro-lens array shows great consistency in size and shape throughout the sample area. We also investigate various optical properties of the micro-lenses evolved glass substrates including the diffraction pattern and diffraction efficiency of light. The glass sample comprising cylindrical micro-lens array can diffract light with moderate diffraction efficiency. We strongly believe that, it is possible to engineer cylindrical micro-lens array on the surface of a variety of transparent materials including glasses and polymers over a large area.
Micro flexible robot hand using electro-conjugate fluid
S. Ueno, K. Takemura, S. Yokota, et al.
An electro-conjugate fluid (ECF) is a kind of functional fluid, which produces a flow (ECF flow) when subjected to high DC voltage. Since it only requires a tiny electrode pair in micrometer size in order to generate the ECF flow, the ECF is a promising micro fluid pressure source. This study proposes a novel micro robot hand using the ECF. The robot hand is mainly composed of five flexible fingers and an ECF flow generator. The flexible finger is made of silicone rubber having several chambers in series along its axis. When the chambers are depressurized, the chambers deflate resulting in making the actuator bend. On the other hand, the ECF flow generator has a needle-ring electrode pair inside. When putting the ECF flow generator into the ECF and applying voltage of 6.0 kV to the electrode pair, we can obtain the pressure of 33.1 kPa. Using the components mentioned above, we developed the ECF robot hand. The height, the width and the mass of the robot hand are 45 mm, 40 mm and 5.2 g, respectively. Since the actuator is flexible, the robot hand can grasp various objects with various shapes without complex controller.
Effect of the subsidiary electrode in a newly developed source lens structure of the microcolumn
Tae-Sik Oh, Dae-Wook Kim, Ho Seob Kim, et al.
A subsidiary electrode was introduced between the extractor and anode in our newly developed source lens design of a micro electron column to improve the probe beam characteristics. At the same field enhancement factor of 3.95, the probe beam current showed a drastic increase compared to that of the conventional source lens structure. The design parameters of the newly developed source lens structure and the equipotential line distribution are presented with simulation results.
Shape optimization of electrostatically driven microcantilevers using simulated annealing to enhance static travel range
R. R. Trivedi, M. M. Joglekar, R. P. Shimpi, et al.
The objective of this paper is to present a systematic development of the generic shape optimization of elec- trostatically actuated microcantilever beams for extending their static travel range. Electrostatic actuators are widely used in micro electro mechanical system (MEMS) devices because of low power density and ease of fab- rication. However, their useful travel range is often restricted by a phenomenon known as pull-in instability. The Rayleigh- Ritz energy method is used for computation of pull-in parameters which includes electrostatic potential and fringing field effect. Appropriate width function and linear thickness functions are employed along the length of the non-prismatic beam to achieve enhanced travel range. Parameters used for varying the thick- ness and width functions are optimized using simulated annealing with pattern search method towards the end to refine the results. Appropriate penalties are imposed on the violation of volume, width, thickness and area constraints. Nine test cases are considered for demonstration of the said optimization method. Our results indicate that around 26% increase in the travel range of a non-prismatic beam can be achieved after optimiza- tion compared to that in a prismatic beam having the same volume. Our results also show an improvement in the pull-in displacement of around 5% compared to that of a variable width constant thickness actuator. We show that simulated annealing is an effective and flexible method to carry out design optimization of structural elements under electrostatic loading.
Optical and thermal characterization on micro-optical elements made by femtosecond laser writing
R. Buividas, V. Mizeikis, G. Kiršanske, et al.
Femtosecond laser polymerization of photonic crystals (PhCs) and diffractive micro-optical elements which can be easily integrated into complex 3D geometries of micro-fluidic chips is analysed in IR spectral domain. Thermal properties of such 3D optical elements and patterns were investigated by thermal imaging, IR spectroscopy and a heat-wave method using absorption-heating with visible light. Thermal imaging allows a simple in situ judgement on a 3D fabrication quality of photonic crystals and is simpler compared with scanning electron imaging. Photonic stop gaps at IR spectral range were clearly observed and IR mapping at the specific spectral wavelength reveals spatial uniformity of PhCs. Potential to use IR imaging with spectral IR plasmonic filters for sensor applications is discussed.
Governing equations for electro-conjugate fluid flow
K. Hosoda, K. Takemura, K. Fukagata, et al.
An electro-conjugation fluid (ECF) is a kind of dielectric liquid, which generates a powerful flow when high DC voltage is applied with tiny electrodes. This study deals with the derivation of the governing equations for electro-conjugate fluid flow based on the Korteweg-Helmholtz (KH) equation which represents the force in dielectric liquid subjected to high DC voltage. The governing equations consist of the Gauss's law, charge conservation with charge recombination, the KH equation, the continuity equation and the incompressible Navier-Stokes equations. The KH equation consists of coulomb force, dielectric constant gradient force and electrostriction force. The governing equation gives the distribution of electric field, charge density and flow velocity. In this study, direct numerical simulation (DNS) is used in order to get these distribution at arbitrary time. Successive over-relaxation (SOR) method is used in analyzing Gauss's law and constrained interpolation pseudo-particle (CIP) method is used in analyzing charge conservation with charge recombination. The third order Runge-Kutta method and conservative second-order-accurate finite difference method is used in analyzing the Navier-Stokes equations with the KH equation. This study also deals with the measurement of ECF ow generated with a symmetrical pole electrodes pair which are made of 0.3 mm diameter piano wire. Working fluid is FF-1EHA2 which is an ECF family. The flow is observed from the both electrodes, i.e., the flow collides in between the electrodes. The governing equation successfully calculates mean flow velocity in between the collector pole electrode and the colliding region by the numerical simulation.
Micro-structured surfaces for algal biofilm growth
It is well known that cells respond to structured surface cues that are on the micro/nanometer scale. Tissue engineering and bio-fouling fields have utilized the semiconductor device fabrication processes to make micro- and nanometer patterned surfaces to study animal cell tissue formation and to prevent algae attachment on marine surfaces respectively. In this paper we describe the use of micro-structured surfaces to study the attachment and growth of algal films. This paper gives an overview of how micro-structured surfaces are made for this purpose, how they are incorporated into a photo bioreactor and how this patterning influences the growth of an algal biofilm. Our results suggest that surface patterning with deeper V-groove patterns that are of the same size scale as the algal species has resulted in higher biomass productivity giving them a chance to embed and attach on the slope and flat surfaces whereas shallower size grooves and completely flat surfaces did not show this trend.
Anti-reflection properties of spherical top nanowire arrays for solar cell applications
Nanowires (NW)/nanopillars (NP) have unique optical and electrical properties that make them attractive for photovoltaic applications. Important factors such as diameter, length and array density of the nanowires have investigated in the recent years or their effect on light trapping. In this work, we study the effect of varying the NWs top tip morphology, and find significant differences in optical response, both via simulations and experiments. In the simulations, optical performance of NW with flat top and spherical top were investigated. The simulated 3D model is a CNT/Cr/a-Si/ITO coaxial structure with total diameter of 760nm. Our results show that as the spacing of the NWgets smaller, the influence of the top morphology on the nanowires’ reflectance becomes more significant. For narrow spacing arrays (p<2d, where p is the period and d is the diameter of NWs) NW device with spherical top shows better antireflection performance than the one with flat top. This is due to the biomimetic antireflection (AR) effect introduced by the spherical top . For large spacing arrays (p<2d), AR effect introduced by spherical tops was almost negligible. It can be ascribed to the low volume concentration of the spherical top comparing to that of the planar surface. In addition, effect of structural defects were also
Development of a multi-electrode system for non-destructive and contactless wafer evaluation
Justin Ndagijmana, Yuki Soh, Junpei Fukashi, et al.
With the miniaturization of CMOS, the gate insulator has extremely become thin until reaching the EOT (equivalent oxide thickness) of less than 1nm in order to keep maintaining high-speed performances of devices and low electric energy consumption. Since the gate insulator is so thin, leakage current increases and the gate dielectric breakdown can easily occur. This affects the reliability of semiconductor devices. To make good devices, it is necessary to use technologies for the evaluation of the gate insulator reliability.

TDDB (Time Dependent Dielectric Breakdown) lifetime has been one of the main factors for this evaluation. In this case, a wafer is destroyed in order to be evaluated, which reduces the semiconductor yield. To solve this problem, we propose a new technique for the evaluation of the gate insulator which is a non-destructive and contactless measurement method, and thus an appropriate method for inline processes.

A voltage is applied on a Si/SiO2 specimen. A voltage source electrode and the specimen are not in contact (10micron gap). After it is charged, the specimen is irradiated by a xenon-flash-lamp. Since the energy of this pulsed light is beyond 4eV, electrons are emitted and move from Si to SiO2. It is possible to estimate the condition (the electrical conductivity) of the insulator using this phenomenon. A multi-electrode system was developed for mass production. With this system, one is able to evaluate 10 thousand points over a 12-inch wafer in 1 minute.
Development of a multi-flash lamp in pulse photo conductivity method
J. Fukashi, J. Ndagijimana, Y. Soh, et al.
In the manufacturing field of semiconductor devices, improvement of yield and increase of throughput is very important issue. Therefore, in the evaluation of semiconductor devices, a method using a light source is frequently used for in-line measurement. In our laboratory, we propose Pulsed Photo Conductivity Method (PPCM) as a device evaluation method for non-destructive and non-contact measurement. To inspect the whole wafer in one minute using PPCM evaluation equipment, high repetition frequency lamp is required .In general, laser is used as light source in device evaluation using light. Laser has a high repetition frequency, but the cost is very high compared with other light sources. Therefore, in this study, we developed a multi-flash system to be used for PPCM evaluation equipment. This system is a high repetition frequency and cheaper. In this study, the maximum repetition frequency of an L11035 Hamamatsu xenon flash lamp used is 530Hz which is not high. Therefore, we developed a light source with high repetition frequency by using several xenon flash lamps in this system.
Investigating extremely low resistance ohmic contacts to silicon carbide using a novel test structure
Yue Pan, Aaron M. Collins, Fahid Algahtani, et al.
Low resistance contracts to highly doped silicon carbide (SiC) are investigated. Using a novel test structure that is easy to fabricate and easy to use, this paper demonstrates how it is used to reliably determine relatively low specific contact resistivities which vary with heat treatment. The test structure requires no error correction and is not affected by parasitic resistances. Using the test structure, small changes in specific contact resistivity are determined for small temperature changes. Results will be presented and discussed on the application of this novel test structure for nickel to highly doped SiC.
Effects of low power microwave radiation on biological activity of Collagenase enzyme and growth rate of S. Cerevisiae yeast
Hamad S. Alsuhaim, Vuk Vojisavljevic, E. Pirogova
Recently, microwave radiation, a type/subset of non-ionizing electromagnetic radiation (EMR) has been widely used in industry, medicine, as well as food technology and mobile communication. Use of mobile phones is rapidly growing. Four years from now, 5.1 billion people will be mobile phone users around the globe - almost 1 billion more mobile users than the 4.3 billion people worldwide using them now. Consequently, exposure to weak radiofrequency/microwave radiation generated by these devices is markedly increasing. Accordingly, public concern about potential hazards on human health is mounting [1]. Thermal effects of radiofrequency/microwave radiation are very well-known and extensively studied. Of particular interest are non-thermal effects of microwave exposures on biological systems. Nonthermal effects are described as changes in cellular metabolism caused by both resonance absorption and induced EMR and are often accompanied by a specific biological response. Non-thermal biological effects are measurable changes in biological systems that may or may not be associated with adverse health effects. In this study we studied non-thermal effects of low power microwave exposures on kinetics of L-lactate dehydrogenase enzyme and growth rate of yeast Saccharomyces Cerevisiae strains type II. The selected model systems were continuously exposed to microwave radiation at the frequency of 968MHz and power of 10dBm using the designed and constructed (custom made) Transverse Electro-Magnetic (TEM) cell [2]. The findings reveal that microwave radiation at 968MHz and power of 10dBm inhibits L-lactate dehydrogenase enzyme activity by 26% and increases significantly (15%) the proliferation rate of yeast cells.
Improved geometrical design of the circular transmission line model ohmic contact test structure
Aaron Collins, Yue Pan, Anthony Holland
This paper proposes a method to determine the design of the Circular Transmission Line Model (CTLM) in order to ensure accurate results are obtained. The CTLM is used to measure the specific contact resistance of a metalsemiconductor barrier. Through analytical modelling it has been shown that the accuracy of the measurements obtained using a particular CTLM pattern, depends on the geometry chosen. By determining which geometries will yield the most sensitive measurement will ensure an accurate result when compared to the sheet resistance and specific contact resistance of an ohmic contact sample. Analysis of the equations reveals that for any given sample a smaller geometry is preferable. This is determined by comparing the differential of specific contact resistance of the sample with the contact end resistance of the test structure. It has been found that for confident results to be obtained then the annular (centre) ring of the structure should be as narrow as is possible within testing constraints.
Optimizing the thermal budget for forming of nickel germanide on crystalline germanium
F. Algahtani, M. Blackford, E. Pirogova, et al.
Nickel germanide is used as a contact material in germanium devices for making low resistance electrical contacts. It forms at relatively low temperatures compared to other germanides. Metal thickness, reaction temperature and duration of temperature are critical parameters. Here we report on the minimum temperature of formation of nickel germanide and on the effect of duration of temperature. Nickel germanide forms rapidly at higher temperatures and more slowly at lower temperatures and below a critical temperature it does not form, for any duration.
Detection of harmful algal bloom causing microalgae using covalently immobilised capture oligonucleotide probes on glass and poly(dimethylsiloxane) surfaces
Karen L. Bruce, Amanda V. Ellis, Sophie C. Leterme, et al.
Harmful algal bloom (HAB) events have been on the rise in the last few decades with some of the causative microalgae exhibiting toxic properties. Therefore, detection is essential in order to prevent mortality of aquatic life and poisoning events from consumption of these biotoxins. Here, oligonucleotide modified glass and poly(dimethylsiloxane) (PDMS) surfaces have been developed for the detection of the HAB causing microalgae, Alexandrium catenella, in a model system. Our preliminary studies show that the glass surface offers superior stability and analytical response when compared to those prepared from PDMS.
Surface acoustic streaming in microfluidic system for rapid multicellular tumor spheroids generation
Layla AlHasan, Aisha Qi, Aswan Al-Aboodi, et al.
In this study, we developed a novel and rapid method to generate in vitro three-dimensional (3D) multicellular tumor spheroids using a surface acoustic wave (SAW) device. A SAW device with single-phase unidirectional transducer electrodes (SPUTD) on lithium niobate substrate was fabricated using standing UV photolithography and wet-etching techniques. To generate spheroids, the SAW device was loaded with medium containing human breast carcinoma (BT474) cells, an oscillating electrical signal at resonant frequency was supplied to the SPUDT to generate acoustic radiation in the medium. Spheroids with uniform size and shape can be obtained using this method in less than 1 minute, and the size of the spheroids can be controlled through adjusting the seeding density. The resulting spheroids were used for further cultivation and were monitored using an optical microscope in real time. The viability and actin organization of the spheroids were assessed using live/dead viability staining and actin cytoskeleton staining, respectively. Compared to spheroids generated using the liquid overlay method, the SAW generated spheroids exhibited higher circularity and higher viability. The F-actin filaments of spheroids appear to aggregate compared to that of untreated cells, indicating that mature spheroids can be obtained using this method. This spheroid generating method can be useful for a variety of biological studies and clinical applications.
Four point probe geometry modified correction factor for determining resistivity
Fahid Algahtani, Karthikram B. Thulasiram, Nashrul M. Nasir, et al.
The four-point probe technique is well known for its use in determining sheet resistance and resistivity (or effective resistivity) of thin films. Using a standard four-point probe setup, relatively large area samples are required. The convention is that the distance from any probe in the probe arrangement should be at least ten times the probe spacing from the sample boundary in order to use the fixed correction factor. In this paper we show, using computer modelling, how accurate measurements can be made using appropriate correction factors for samples that are either small or of any thickness. For the significant extent of variations used, the correction factor does not vary significantly.
Modelling and fabrication of thermally actuated micropores for biological sensing
Thermal bimorphs are extensively used in engineering applications with its ability to generate large forces and deflections. A new pore-structured thermal microactuator design, which incorporates the thermal bimorph concept, is proposed to trap single biological cells for sensing and imaging. This can act as an alternative to the existing methods as it possesses the potential to trap the cells without any repercussions while being relatively low cost and easy to operate. In this study, the thermal microactuator design is investigated and analysed using finite element analysis (FEA) where the deflection was determined to be dependent on the effective length and the coefficients of thermal expansion (CTE). Upon thermal loading, the internal stresses were found to be tunable by employing several geometric modifications. With determined parameters, prototypes of the design were fabricated on silicon nitride (Si3N4) membrane with Polydimethylsiloxane (PDMS) coating.
Assessment of GeB doped SiO2 optical fiber for the application of remote radiation sensing system
A. Alawiah, M. M. Fadhli, S. Bauk, et al.
The research and development efforts on the silica (SiO2) optical fiber for application in radiation sensing and other dosimetry field have become quite active. The widely used LiF based dosimeter (TLD) has shown a relatively low reproducibility and there is a time delay in dose assessment which loses its capability as direct real-time dose assessment dosimeters unlike diodes. The macroscopic size of the optical fiber generally does not allow direct in vivo dose sensing in the inner organ for radiotherapy and medical imaging. A flat optical fiber (FF) with nominal dimensions of (0.08 x10 x 10) mm3 of pure silica SiO2 and GeO2 with Boron doped silica fiber SiO2 was selected for this research. The Germanium was used a dopant to enhance the flat optical fiber to reach much higher responsiveness and dose sensitivity in high energy and high dose irradiation. Together with this combination, both TLD dimension and dose assessment issues was hoped to be overcome. The research conducted by comparing the response of pure silica SiO2 flat optical fiber with a GeO2 with Boron doped silica SiO2 flat optical fiber. The FF sample was annealed at 400°C for one hour before irradiated. Kinetic parameters and dosimetric glow curve of TL response and sensitivity were studied with respect to the electron beam of high dose of micro beam irradiation of 1.0 kGy, 5.0 kGy, 10.0 kGy, 50.0 kGy, 100.0 kGy, 500.0 kGy, and 1.0 MGy using Singapore Synchrotron Light Source’s (PCIT) beamline. The PCIT operates at 500mA current with real time current range from 90-100mA, dose rate of 3.03 MGy/hour and energy at 8.9KeV. The source to Source Surface Distance (SSD) was at 6.0 cm, with a field size of 20mm × 8mm diameter of a half circle. The TL response was measured using a TLD reader Harshaw Model 3500. The Time-Temperature-Profile (TTP) of the reader was obtained to a preheat temperature of 150 °C for 5 s, the output signal being acquired at a temperature ramprate of 35 °Cs-1, acquisition time of 10 s and a maximum temperature of 400 °C each of the FF samples. All reading was taken under N2 gas flow, suppressing oxidation and potential triboluminescence. The proposed FF shows the excellent TL response for high energy irradiation and good reproducibility and exhibits a very low rate of fading and low variation background signal. From these results, the proposed FF can be used as a radiation dosimeter in remote radiation sensing and favorably compares with the widely used of LiF based dosimeter on common medical radiotherapy application.
Hydrophobicity studies of polymer thin films with varied CNT concentration
N. H. M. Rodzi, M. M. Shahimin, P. Poopalan, et al.
Surface functionalization studies for re-creating a ‘Lotus Leaf’ effect (superhydrophobic) have been carried out for the past decade; looking for the material which can provide high transparency, low energy surface and high surface roughness. Fabrication of polydimethylsiloxane (PDMS) and multiwalled carbon nanotubes (MWCNT) hybrid thin film variations on glass to produce near-superhydrophobic surfaces is presented in this paper. There are three important parameters studied in producing hydrophobic surfaces based on the hybrid thin films; concentration of PDMS, concentration of MWCNT and droplet sizes. The study is carried out by using PDMS of varied cross linker ratio (10:1, 30:1 and 50:1) with MWCNT concentration of 1mg, 10mg and 15mg for 0.5 μl, 2.0 μl, 5.0 μl and 10 μl droplet sizes. The resulting hybrid thin films show that hydrophobicity increased with increasing cross linker ratio and MWCNT percentage in the PDMS solution. A near superhydrophobic surface can be created when using 15 mg of MWCNT with 50:1 cross linker ratio PDMS thin films, measured on 10 μl droplet size. The hybrid thin films produced can be potentially tailored to the application of biosensors, MEMS and even commercial devices.
Investigation of amorphisation of germanium using modeling and experimental processes
S. Almalki, F. Algahtani, M. Blackford, et al.
Crystalline germanium substrates were amorphised to a depth of one micron by ion implantation of germanium ions at a series of relatively high energies and dose. Using the ion implantation modeling software TRIM, this paper compares the amorphisation results from the ion implantation simulations and experimental results from transmission electron microscopy (TEM) analysis of cross-sections of implanted samples. TEM cross-section micrographs show a clear boundary between amorphous and crystalline germanium. The effect of amorphisation of Ge on the subsequent formation of Nickel germanide is demonstrated and one significant issue is the increased depth of NiGe grains formed on a-Ge compared with c-Ge.
Preparation of Cu2O/TiO2 nanotube heterojunction arrays with enhanced photoelectrocatalysis performance
Jianfang Zhang, Yan Wang, Tiankuo Shen, et al.
Highly ordered TiO2 nanotube arrays (TNAs) were firstly fabricated by two-step anodization process. Then the Cu2O nanoparticles were deposited onto the as-fabricated TNAs via potentiostatic electrochemical deposition method in a three-electrode cell (the TNAs, Ag/AgCl and graphite performed as working electrode, reference electrode and counter electrode, respectively). The field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were adopted for the morphology characterization, the crystalline phases and composition analyzation of the as-prepared Cu2O/TNAs heterojunctions, repectively. The photoelectrochemical performance of the Cu2O/TNAs samples was evaluated by measuring the enhanced photocurrent response under intermittent Xe lamp irradiation. Then the photocatalytic properties were further investigated based on the photocatalytic degradation of methyl orange (MO) solution under simulated visible light. The results indicated that the inner surface and interface of the TNAs had been successfully modified with uniformly distributed Cu2O nanoparticles, which further ameliorated the photoelectrochemical and photocatalytic activities.
Green synthesis of silver nanoparticles as antibacterial agent using Rhodomyrtus tomentosa acetone extract
Supayang Piyawan Voravuthikunchai, Julalak Chorachoo, Lily Jaiswal, et al.
The capability of Rhodomyrtus tomentosa acetone extract (RAE) for the production of silver nanoparticles (AgNPs) has been explored for the first time. Silver nanoparticles with a surface plasmon resonance band centered at 420-430 nm were synthesized by reacting RAE with AgNO3. Reaction time, temperature, concentration of AgNO3 and RAE could accelerate the reduction rate of Ag+ and affect AgNPs size. The nanoparticles were found to be 10-30 nm in size and spherical in shape. XRD data demonstrated crystalline nature of AgNPs dominated by (200) facets. FTIR results showed decrease in intensity of peaks at 3394, 1716 and 1618 cm-1 indicating the involvement of O-H, carbonyl group and C=C stretching with the formation of AgNPs with RAE, respectively. The C-O-C and C-N stretching suggested the presence of many phytochemicals on the surface of the nanoparticles. High negative zeta potential values confirmed the stability of AgNPs in water. In vitro antibacterial activity of AgNPs was tested against Staphylococcus aureus using broth microdilution method. AgNPs capped with RAE demonstrated profound antibacterial activity against the organisms with minimum inhibitory concentration and minimum bactericidal concentration in the range between 3.1-6.2 and 6.2-50 μgmL-1, respectively. The synthesized nanoparticles could be applied as an effective antimicrobial agent against staphylococcal infections.
Spectroscopic modeling of water molecule
R. I. Danylo, B. A. Okhrimenko
This research is devoted to the vibrational spectroscopy inverse problem solution that gives a possibility to design a molecule and make conclusions about its geometry. The valence angle finding based on the usage of inverse spectral vibrational spectroscopy problem is a well-known task. 3N-matrix method was chosen to solve the proposed task. The usage of this method permits to make no assumptions about the molecule force field, besides it can be applied to molecules of matter in liquid state. Anharmonicity constants assessment is an important part of the valence angle finding. The reduction to zero vibrations is necessary because used matrix analytical expression were found in the harmonic approach. In order to find the single-valued inverse spectral problem of vibrational spectroscopy solution a shape parameter characterizing “mixing” of ω1 and ω2 vibrations forms must be found. The minimum of such a function Υ called a divergence parameter was found. This function characterizes method’s accuracy. The valence angle assessment was reduced to the divergence parameter minimization. The β value concerning divergence parameter minimum was interpreted as the desired valence angle. The proposed method was applied for water molecule in liquid state: β = (88,8 ±1,7)° . The found angle fits the water molecule nearest surrounding tetrahedral model including hydrogen bond curvature in the first approximation.