This PDF file contains the front matter associated with SPIE Proceedings Volume 6886, including the Title Page, Copyright information, Table of Contents, Conference Committee listing, Introduction, and Plenary Paper.

In-Check is STMicroelectronics proprietary platform for molecular diagnostics. In-Check lays its foundations on the monolithic integration of microelectronics and micromachining technology MEMS, with microfluidic and optical features, bio-chemical surface functionalization and molecular biology. It comprises a core lab-on-chip device, control and reading instrumentation, a complete suite of software modules, and application protocols. Leveraging on such capabilities, In-Check enables fast, highly sensitive and specific, multi-analytical capability of nucleic acid analysis. The platform provides a unique combination of nucleic acid amplification, by polymerase-chain-reaction and target identification and typing by DNA microarray. These integrated biological functionalities together with top quality standard and process control are key features for a platform to be accepted by the highly demanding modern medical diagnostic. This paper describes recent developments of In-Check and some core biological characterizations.

The development of surface-active biochips for control of fluorescence within microscopy platforms is described. These use surface-plasmon control to provide selective excitation of fluorescently labeled, live cell populations. These chips effectively combine a number of commonly used techniques such as SPR, TIRF and epi-fluorescence within a single device and have the potential to provide sub-cellular discrimination of excitation in 3-D. Thus within a single field of view we can selectively excite membrane versus cytoplasm and localise the excitation within the lateral plane to an area of a few square microns.

We have developed components of a diagnostic disposable platform that has the dual purpose of providing molecular diagnostics at the point of care (POC) as well as stabilizing specimens for further analysis via a centralized surveillance system. This diagnostic is targeted for use in low-resource settings by minimally trained health workers. The disposable device does not require any additional instrumentation and will be almost as rapid and simple to use as a lateral flow strip test - yet will offer the sensitivity and specificity of nucleic acid amplification tests (NAATs). The low-cost integrated device is composed of three functional components: (1) a sample-processing subunit that generates clean and stabilized DNA from raw samples containing nucleic acids, (2) a NA amplification subunit, and (3) visual amplicon detection sub-unit. The device integrates chemical exothermic heating, temperature stabilization using phase-change materials, and isothermal nucleic acid amplification. The aim of developing this system is to provide pathogen detection with NAAT-level sensitivity in low-resource settings where there is no access to instrumentation. If a disease occurs, patients would be tested with the disposable in the field. A nucleic acid sample would be preserved within the spent disposable which could be sent to a central laboratory facility for further analysis if needed.

We have investigated the utilization of particle agglutination assays using forward light scattering measurements in a microfluidic device towards detecting viral particles. The model viral target was bovine viral diarrhea virus (BVDV). Highly carboxylated polystyrene microspheres (510 nm) were coated with anti-BVDV monoclonal antibodies. This solution was in turn used to detect live modified BVDV. This assay was first performed in a two well slide for proof of concept and then in a simple y-channel microfluidic device with optical fibers arranged in a close proximity setup. Particle immunoagglutination was detected through static light scattering measurements taken at 45° to incident light. In the microfluidic device, modified live BVDV was detected with a detection limit of 0.5 TCID₅₀ mL^-1.

A RF wireless capacitive flow sensor is developed. The sensor has integrated inductor with the flow sensitive capacitors as LC circuit. The resonant frequency of the sensor changes as the capacitance changes with applied flow. The sensor uses LPCVD silicon nitride as sensitive membrane and the residual stress of the membrane has been measure as 139 MPa. The sensor has size of 10 mm × 4 mm × 0.5 μm. The sensor integrated two pressure sensors together and designed related to flow 5-20ml/hour. The deflection of different shape of membranes and the parameters of flow sensor sensitivity are discussed. The deflection of square membrane is 130% to circular membrane under same applied pressure.

We have developed fabrication techniques for creating suspended electrically addressable MEMS structures in microfluidic channels, as well as monolithic integration of sensors within microfluidic devices. As we will demonstrate, creative use of state-of-the-art MEMS fabrication techniques allows the integrated manufacturing of a number of sensors, for simultaneous measurement of, for example, flow velocity, thermal conductivity and normal stress. We will demonstrate the versatility of these techniques with an example of capillary viscosity sensor integrating independent flowrate, temperature, and pressure drop sensors.

This article presents design and development of a novel 3D micromirror for large deflection scanning application in invivo optical coherence tomography (OCT) bio-imaging probe. Overall mirror chip size is critical to reduce the diameter of the probe; however, mirror plate itself should not be less than 500 μm as smaller size means reducing the amount of light collected after scattering for OCT imaging. In this study, mirror chip sizes of 1 × 1 mm² and 1.5 × 1.5 mm² were developed with respectively 400 and 500 micrometer diameter mirror plates. The design includes electro thermal excitation mechanism in the same plane as mirror plate to achieve 3D free space scanning. Larger deflection requires longer actuators, which usually increase the overall size of the chip. To accommodate longer actuators and keep overall chip size same curved beam actuators are designed and integrated for micromirror scanning. Typical length of the actuators was 800 micrometer, which provided up to 17 degrees deflection. Deep reactive ion etching (DRIE) process module was used extensively to etch high aspect ratio structures and keep the total mirror chip size small.

Massively parallel nanofluidic systems are lab-on-a-chip devices where solution phase biochemical and biological analyses are implemented in high density arrays of nanoliter holes micro-machined in a thin platen. Polymer coatings make the interior surfaces of the holes hydrophilic and the exterior surface of the platen hydrophobic for precise and accurate self-metered loading of liquids into each hole without cross-contamination. We have created a "nanoplate" based on this concept, equivalent in performance to standard microtiter plates, having 3072 thirty-three nanoliter holes in a stainless steel platen the dimensions of a microscope slide. We report on the performance of this device for PCR-based single nucleotide polymorphism (SNP) genotyping or quantitative measurement of gene expression by real-time PCR in applications ranging from plant and animal diagnostics, agricultural genetics and human disease research.

This paper presents the design and fabrication of MEMS based Coulter counter for monitoring cellular volumetric changes after an exposure to various media. The design consists of a thick SU8 channel which is divided into mixing, focusing, and measuring regions. The mixing region is a serpentine shaped channel, enabling complete mixing of a sample and a reactant before entering the focusing region. The focusing region consists of an electrode pair used to generate AC fields that result in negative dielectrophoretic forces directing cells from all directions to the center of the channel to prevent clogging of the Coulter channel. Finally, the measuring region consists of a channel of width ranging from 20-25 μm, with multiple electrode pairs fabricated using electroplated gold in order to measure the change in impedance at different points along the channel as a cell passes through. This device improves upon existing macro-scale Coulter counter technology by allowing extremely small sample sizes (10¹ compared to 10⁵ cells per experiment), an extremely short time frame from the exposure to reactant media to the initial measurement, serial time series measurements of a single cell, and optical microscopic monitoring of the experiment. The design of this chamber will allow for the manufacture of cell specific channel diameters in order to maximize measurement precision for each cell type. This design also eliminates the sheath flow and complex fluid control systems that make conventional cytometers bulky and complicated.

Pathogenic bacterial cell detection is currently performed using techniques such as culture enrichment and various plating methods, which are expensive and can take up to several days. In this study, we describe the design, fabrication, and testing of a rapid and inexpensive sensor for detection of target cells electrically in real-time. The sensor operates with the use of microelectrodes integrated in a micro-channel. As a proof of principle, we have successfully demonstrated real-time detection of target yeast cells with a concentration of 10⁷ cells/ml. We have also demonstrated the selectivity of our sensors in responding to target cells while remaining irresponsive to non-target cells. We also perform theoretical modeling in order to determine the ultimate detection limit of the sensor. Based on our modeling results, proper optimization of the sensor can yield detection limits approaching the single cell level.

We present a compact portable chip-based capillary electrophoresis system that employs capacitively coupled contactless conductivity detection (C⁴D) operating at 4 MHz as an alternative detection method compared to the commonly used optical detection employing laser-induced fluorescence. The disposable chip for this system is fabricated out of PMMA using injection molding; the electrodes are screen-printed or thin-film electrodes. The system allows the measurement of small ions like Li, Na, K typically present in foodstuff like milk and mineral water as well as acids in wine.

We demonstrate the fabrication of three-dimensional (3D) hollow microstructures embedded in photostructurable glass by a nonlinear multiphoton absorption process using a femtosecond (fs) laser. Fs laser direct writing followed by annealing and successive wet etching in dilute hydrofluoric (HF) acid solution resulted in the rapid manufacturing of microchips with 3-D hollow microstructures for the dynamic observation of living microorganisms in fresh water. The embedded microchannel structure enables us to analyze the continuous motion of Euglena gracilis and Dinoflagellate. Such microchips, referred to as nano-aquariums realize the efficient and highly functional observation of microorganisms.

Previously, we proposed novel microvalve structures, amenable to bulk micromachining, which demonstrated fully complementary behavior. Two distinct microvalves were devised, one analogous to the p-MOSFET, and the other analogous to the n-MOSFET found in complementary MOSFET devices and circuits. Ring oscillator behavior based on digital NOR logic gates was described, for both micro-pneumatics (based on compressible gas flow) and micro-hydraulics (based on incompressible liquid flow). In this work, micro-pneumatic analog circuits are described, based on the previously-described complementary digital pneumatic microvalve devices. In particular, a micro-pneumatic operational amplifier is described and simulated in detail. Also, prospects for energy harvesting or scavenging based on micro-pneumatic circuits are discussed.

We present a novel self-aligned and hybrid polymer fabrication process for an electro-enzymatic glucose sensor. The self-aligned fabrication process is performed using polydimethylsiloxane (PDMS) as a process substrate material, SU-8 as a sensor structural material, and gold as an electrode material. PDMS has many advantages as a process substrate over conventional substrates such as bare silicon or glass. During the fabrication process, SU-8 has good adhesion to the PDMS. However, after completion of all fabrication steps, the SU-8 based sensors can be easily peeled-off from the PDMS. The PDMS is prepared on a glass handle wafer, and is reusable for many process cycles. Such an SU-8 release technique from a PDMS substrate has never been proposed before. The novel process is employed to realize a glucose sensor with active and reference gold electrodes that are sandwiched between two SU-8 layers with contact pad openings and the active area opening to the top SU-8 layer. The enzyme glucose oxidase is immobilized within the confined active area opening to provide an active electrode sensing surface. After successful fabrication using the hybrid process, the overall thickness of the sensors is measured between 166.15 μm and 210.15 μm. The sensor area and the electrode area are 2mm x 3mm and 2mm x 2mm respectively. The resulting glucose sensors are mechanically flexible. A linear response is observed for the glucose sensors, typically between 50mg/dl and 600mg/dl glucose concentrations.

This paper presents the design and fabrication of an integrated cell counter for a MEMS flow cytometer. The imbedded out-of-plane micro lens in the cell counter is used to focus the fluorescent or scattering light emitting from the dyed cells into the output fiber to improve the optical detection efficiency. Both the optical cell counter device with imbedded micro-lens and the hydro-focusing unit of the micro flow cytometer were fabricated using a process based on UV lithography of SU-8 negative-tone photoresist. A novel microfabrication technology based on tilted UV-lithography and controlled exposure dosage and development time was performed to produce the out-of-plane micro lens. Out-of-plane micro lens with various pad sizes and focal lengths can be fabricated by carefully controlling the fabrication process. The microlens and the hydrofocusing unit were fabricated using the same mask. High alignment accuracy can therefore be achieved without any post-fabrication alignment processes.

The objective of this study is to present chaotic micromixers in which a series of microstructures are placed on the top and bottom floors of channels. Passive micromixers fabricated by MEMS technologies with crosswise grooves and ridges are considered. Numerical simulations using the commercial software CFD-ACE(U) are employed to predict the effects of various patterns of microstructures on mixing efficiency with the range of Reynolds number from 0.05 to 50. The influences of non-dimensional parameters such as the Reynolds number as well as the geometrical parameters on the mixing performance are presented in terms of the mixing index. Micromixers which are made of PDMS are used to investigate the mixing characteristics influenced by the different kinds of microstructures. A significant amount of stirring resulting from chaotic mixing can be seen due to the fluids flowing through the crosswise ridges embedded on the top and bottom floors of channels. While Re is greater than 1, the mixing index of the micromixer with crosswise ridges starts to increase as Re increases. This means that the flow field in this micromixer results in efficient chaotic mixing. Simulation results are presented to compare with the experimental data, and a very good agreement can be achieved. Finally, various numbers of the crosswise ridges with the same orientation in one cycle of the channels are investigated to present to the mixing performance in the microchannels. An optimal design can be found in our works.

Micro fluidic package with integrated reservoirs has been developed for DNA /RNA extraction application. A membrane based pump which consists of a reservoir to store reagents and a pin valve to control the fluid is developed to dispense the reagents into the chip. A programmable external actuator is fabricated to dispense the fluid from the membrane pump into the DNA chip. An elastic and high elongation thin rubber membrane is used to seal the membrane pump and at the same time prevent actuator from mixing with different reagents in the micro fluidic package. Break displacement during actuation of membrane pump sealing material is studied with different ratios of PDMS and other types of rubber materials. The fluid flow from the reservoir to the chip is controlled by a pin valve which is activated during the external actuation. A CFD simulation is performed to study the pumping action dusting the external actuation and is validated with experimental results.

DNA analysis, specifically single nucleotide polymorphism (SNP) detection, is becoming increasingly important in rapid diagnostics and disease detection. Temperature is often controlled to help speed reaction rates and perform melting of hybridized oligonucleotides. The difference in melting temperatures, Tm, between wild-type and SNP sequences, respectively, to a given probe oligonucleotide, is indicative of the specificity of the reaction. We have characterized Tm's in solution and on a solid substrate of three sequences from known mutations associated with Cystic Fibrosis. Taking advantage of Tm differences, a microheater array device was designed to enable individual temperature control of up to 18 specific hybridization events. The device was fabricated at Sandia National Laboratories using surface micromachining techniques. The microheaters have been characterized using an IR camera at Sandia and show individual temperature control with minimal thermal cross talk. Development of the device as a real-time DNA detection platform, including surface chemistry and associated microfluidics, is described.

Here, interconnection technique to link digital microfluidic chips is proposed. Three kinds of digital microfluidic modules with connecting interface, including flexible module and two types of connector modules, are designed and fabricated. Since these modules are fabricated on a compliant polymer-based substrate (ITO PET), chip-to-chip droplet transportation even at different planes can be achieved by the proposed technique. A low-temperature fabrication process is developed for the polymer substrates, where the SU-8 acts as the insulator. Droplet transportation through electrowetting on curved surface is confirmed by testing on the bended flexible modules with different curvatures from 0 to 0.06 mm^-1 at around 70 V_AC. Then the droplet transportations between flexible and connector modules are investigated. It is found that the gap size between two modules and the sidewall profiles at interface affect the droplet transportation directly. For the gap size around 50μm with a smooth perpendicular sidewall profile, 80 V_AC is shown to actuate droplet of 1.5 μl, 2.5 μl, or 3.5 μl to cross over the interface successfully.

Nanoparticles have potential applications in many areas such as consumer products, health care, electronics, energy and other industries. As the use of nanoparticles in manufacturing increases, we anticipate a growing need to detect and measure particles of nanometer scale dimensions in fluids to control emissions of possible toxic nanoparticles. At present most particle separation techniques are based on membrane assisted filtering schemes. Unfortunately their efficiency is limited by the membrane pore size, making them inefficient for separating a wide range of sizes. In this paper, we propose a passive spiral microfluidic geometry for momentum-based particle separations. The proposed design is versatile and is capable of separating particulate mixtures over a wide dynamic range and we expect it will enable a variety of environmental, medical, or manufacturing applications that involve rapid separation of nanoparticles in real-world samples with a wide range of particle components.

In microflows where Reynolds number is much smaller than unity, screwing motion of spirals is an effective mechanism of actuation as proven by microorganisms which propel themselves with the rotation of their helical tails. The main focus of this study is to analyze the flow enabled by means of a rotating spiral inside a rectangular channel, and to identify effects of parameters that control the flow, namely, the frequency and amplitude of rotations and the axial span between the helical rounds, which is the wavelength. The time-dependent three-dimensional flow is modeled by Stokes equation subject to continuity in a time-dependent deforming domain due to the rotation of the spiral. Parametric results are compared with asymptotic results presented in literature to describe the flagellar motion of microorganisms.

This work primarily aims to integrate dissolved oxygen sensing capability with a microfluidic platform containing arrays of micro bio-reactors or bio-activity indicators. The measurement of oxygen concentration is of significance for a variety of bio-related applications such as cell culture and gene expression. Optical oxygen sensors based on luminescence quenching are gaining much interest in light of their low power consumption, quick response and high analyte sensitivity in comparison to similar oxygen sensing devices. In our microfluidic oxygen sensor device, a thin layer of oxygen-sensitive luminescent organometallic dye is covalently bonded to a glass slide. Micro flow channels are formed on the glass slide using patterned PDMS (Polydimethylsiloxane). Dissolved oxygen sensing is then performed by directing an optical excitation probe beam to the area of interest within the microfluidic channel. The covalent bonding approach for sensor layer formation offers many distinct advantages over the physical entrapment method including minimizing dye leaching, ensuring good stability and fabrication simplicity. Experimental results confirm the feasibility of the device.

A flexible enclosure for fluidic sealing of SU-8 microcomponents was developed using polydimethylsiloxane (PDMS). The flexible enclosure can be mechanically assembled to SU-8 microchannels even in the presence of liquid. The seal is mechanical and completely reversible, thus allowing the channels to already contain immobilized enzymes or cells prior to assembly. To provide such a reversible fluid tight lid, the PDMS and SU-8 substrates contain interlocking structures that facilitate assembly and sealing together of the two substrates. Interlocking 1 mm ridges/holes and 400 μm ridges/grooves were fabricated on PDMS and SU-8 surfaces that hold the two pieces in place to prevent PDMS lid and SU-8 microchannels separation during handling and fluid flow. Furthermore, a 20 μm bump on the PDMS surface, which has the same width and length dimensions as the 400 μm deep SU-8 microchannel, acts as a plug to keep the fluid within the microchannel and prevent leakage between the PDMS-SU-8 interface. The assembled microchannels and enclosures can withstand manually applied fluidic pressure via a syringe which is noticeably higher than channels with a simple lid and no interconnect structures. The device was additionally quantified for pressure versus flow rate using a syringe pump and pressure sensor. The seal remained leak free up to 0.6 ml/min and 2.36 kPa. In addition, a preliminary cell viability test was conducted with leukemia cells and we observed that cells lived in the channel microenvironment for 24 hours.

We present magnetically-actuated micromechanical interconnects for microfluidic applications fabricated in-house using PDMS-iron elastomer-ferromagnetic composites (EFCs). Interconnects are fluid-tight, interlocking cylindrical posts and holes whose assembly can be made easier by magnetically actuating the EFC cylinders via axial extension and radial contraction. Towards this goal, we demonstrate magnetic actuation of interconnect structures, and quantify the mechanical disassembly of PDMS-iron interconnects without an applied magnetic field. Previously, we showed the mechanical assembly and disassembly of hybrid combinations of non-magnetic SU-8, silicon, and polydimethylsiloxane (PDMS) microfluidic interconnects. We fabricate EFCs for our interconnects by embedding iron microspheres (<63% by weight) in PDMS. We employed permanent magnets to create 0.045-0.065T constant fields, along with an optics test set-up that included a diode laser and magnification to quantify micron-sized deflections. The interconnects exhibited radial contractions of 3-12% and axial elongation of 2-11%. Without the magnetic field, disassembly forces of 36-71mN were measured by a controlled force linear actuator for PDMS-iron cylinders from PDMS and PDMS-iron holes. This work shows promise for radial contraction of cylinders for assembly with lower forces while maintaining high disassembly forces once the interconnects are assembled and the magnetic field is removed.

MicroPlumbers Microsciences LLC, has developed a relatively simple concentrator device based on isothermal evaporation. The device allows for rapid concentration of dissolved or dispersed substances or microorganisms (e.g. bacteria, viruses, proteins, toxins, enzymes, antibodies, etc.) under conditions gentle enough to preserve their specific activity or viability. It is capable of removing of 0.8 ml of water per minute at 37°C, and has dimensions compatible with typical microfluidic devices. The concentrator can be used as a stand-alone device or integrated into various processes and analytical instruments, substantially increasing their sensitivity while decreasing processing time. The evaporative concentrator can find applications in many areas such as biothreat detection, environmental monitoring, forensic medicine, pathogen analysis, and agricultural industrial monitoring. In our presentation, we describe the design, fabrication, and testing of the concentrator. We discuss multiphysics simulations of the heat and mass transport in the device that we used to select the design of the concentrator and the protocol of performance testing. We present the results of experiments evaluating water removal performance.

A passive pumping for lab-on-a-chip using surface tension only is the most effective method because the effect of surface tension on a flow is significant in microscale. The movement of the triple point at a meniscus is driven by surface tension, resisted by viscous stress, and balanced by inertial force. In previous studies, the meniscus motion has been predicted theoretically with one-dimensional model. However, three-dimensional flow field around the meniscus and the effect of cross-sectional shapes on the flow have not assessed yet. Here, we visualized and analyzed the surfacetension- driven blood flow using spectral-domain Doppler optical coherence tomography.

Due to the proper optical property and flexibility in the process development, an epoxy-based, high-aspect ratio photoresist SU-8 is now attracting attention in optical sensing applications. Manipulation of the surface properties of SU-8 waveguides is critical to attach functional films such as chemically-sensitive layers. We describe a new integration process to immobilize fluorescence molecules on SU-8 waveguide surface for application to intensity-based optical chemical sensors. We use two polymers for this application. Spin-on, hydrophobic, photopatternable silicone is a convenient material to contain fluorophore molecules and to pattern a photolithographically defined thin layer on the surface of SU-8. We use fumed silica powders as an additive to uniformly disperse the fluorophores in the silicone precursor. In general, additional processes are not critically required to promote the adhesion between the SU-8 and silicone. The other material is polyethylene glycol diacrylate (PEGDA). Recently we demonstrated a novel photografting method to modify the surface of SU-8 using a surface bound initiator to control its wettability. The activated surface is then coated with a monomer precursor solution. Polymerization follows when the sample is exposed to UV irradiation, resulting in a grafted PEGDA layer incorporating fluorophores within the hydrogel matrix. Since this method is based the UV-based photografting reaction, it is possible to grow off photolithographically defined hydrogel patterns on the waveguide structures. The resulting films will be viable integrated components in optical bioanalytical sensors. This is a promising technique for integrated chemical sensors both for planar type waveguide and vertical type waveguide chemical sensors.

In this paper, the design, modeling, fabrication and characterization of a planar passive microfluidic mixer capable of mixing particulate laden flows at low Reynolds numbers (Re) is reported. Particle-based flow modeling was performed using CFD-ACE+ software to simulate micromixer designs for efficient particle dispersion across microchannel cross-section. The micromixer design developed herein incorporates rectangular shaped obstructions within the microchannel to propel both the particles within the flow and the flow itself into the other half of the channel, thereby achieving mixing. A simple technique to analyze and quantify particle mixing is also proposed. The developed particle micromixer has a simple planar structure, thereby resulting in easy realization and integration with on-chip microfluidic systems, such as micro total analysis systems or lab-on-a-chip.

Mycobacterium Avium Complex (MAC) is an opportunistic pathogen that threatens public health and has high clinical relevance. While culture-based and molecular biology techniques for identification are available, these methods are prone to error and require weeks to perform. There is a critical need for improved portable lab-on-a-chip sensor technology which will enable accurate and rapid point-of-care detection of these microorganisms. In this work, a new capacitive sensing strategy is explored utilizing interdigitated array (IDA) microelectrodes and exploiting the paraffinophilic nature of MAC. In this approach, paraffin wax is deposited over IDA microelectrodes to selectively extract these microorganisms from samples. As bacteria consume the dielectric paraffin layer, the charging current of the IDA capacitor changes to facilitate detection. Several IDA geometries were designed and simulated using CFD-ACE+ modeling software and compared with mathematical models. Capacitance of fabricated devices was determined using a charge-based capacitance measurement (CBCM) technique. Modeling and experimental results were in good agreement. Detection of femto-Farad changes in capacitance is possible, making this a feasible technique for sensing small changes in the paraffin for detection of paraffinophilic MAC.

Microporous structures are a common theme in biomedical devices, microfluidics, geology and other fields of study. However because of the complexity and lack of symmetry, it has been difficult to fabricate 3D arbitrary microporous structures with broad-illumination photolithography. We apply two-photon polymerization and femtosecond laser directwriting techniques to fabricate 3D microporous structures in photopolymers. Three dimensions are built up from 2D patterned-microchannels with random geometry. The height and the width of the features are about 40 μm and 5 μm, respectively. We make 3D microchannels with random apertures and obstacles in two layers that allow liquid to flow through multiple random flowpaths. We also fabricate three-layered lattice-like microstructures. In each layer, the height and the width of the walls are about 18 μm and 2 μm, respectively. Our current application of these microporous structures is for a fundamental study of internal fluid interfaces in microfluidic systems during imbibition and drainage, using interfacial areas per volume as a measure of internal energy density as a function of saturation and capillary pressure.

The purpose of this study is to generate monodisperse oil-in-water (O/W) and water-in-oil (W/O) emulsions using microfluidic T-junction. The materials of poly methyl methacrylate (PMMA) (hydrophobic), polydimethylsiloxane (PDMS) (hydrophobic) and glass (hydrophilic) were employed for microfluidic chip fabrication. Our strategy is based on the shear focus effect and sheath effect (focusing) to form uniform self-assembling sphere structures, the so-called O/W and W/O emulsions, in the T-junction microchannel. Results show that the size from 31 μm to 43 μm in diameter of O/W emulsions was generated by using the glass-based microfluidic chip. In addition, results show that the size from 70 μm to 220 µm of W/O emulsions was available by utilizing the PMMA-based microfluidic chip. These W/O emulsions were further applied to Ca-alginate microparticles (Ca-alg MPs). And the results also show that the size from 410 μm to 700 μm of UV-Photopolymerized microparticles was available by utilizing the PDMS-based microfluidic chip. The proposed microfluidic chips are capable of generating relatively uniform micro-droplets and have the advantages of actively controlling the droplet diameter, and having a simple and low cost process, with a high throughput.