This PDF file contains the front matter associated with SPIE Proceedings Volume 7683, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Nanostructured materials have triggered a great excitement in recent times due to both fundamental interest as well as technological impact relevant for lithium ion batteries (LIBs). Size reduction in nanocrystals leads to a variety of unexpected exciting phenomena due to enhanced surface-to-volume ratio and reduced transport length. We will consider a few examples of nanostructured electrode materials in the context of lithium batteries for achieving high storage and high rate performances: 1) LiFePO₄ nanoplates synthesized using solvothermal method could store Li-ions comparable to its theoretical capacity at C/10, while at 30C, they exhibit storage capacity up to 45 mAh/g. Size reduction (~30 nm) at the b-axis favors the fast Li-ion diffusion. In addition to this, uniform ~5 nm carbon coating throughout the plates provides excellent electronically conducting path for electrons. This nano architecture enables fast insertion/extraction of both Li-ions as well as electrons; 2) Mesporous-TiO₂ with high surface area (135m²/g) synthesized using soft-template method exhibits high volumetric density compared to commercial nanopowder (P25), with excellent Li-storage behavior. C16 meso-TiO₂ synthesized from CTAB exhibits reversible storage capacity of 288mAh/g at 0.2C and 109 mAh/g at 30C; 3) Zero strain Li₄Ti₅O₁₂ anode material has been synthesized using several wet chemical routes. The best condition has been optimized to achieve storage capability close to theoretical limit of 175mAh/g at C/10. At 10C, we could retain lithium storage up to 88 mAh/g; 4) We report our recent results on α-Fe₂O₃ and γ-Fe₂O₃ using conversion reaction, providing insight for a better storage capability in γ-phase than the α-phase at 2C resulting solely from the nanocrystallinity.

Recent work in our laboratory has been directed towards development of mixed layered transition metal oxides with general composition Li[Ni, Co, M, Mn]O₂ (M=Al, Ti) for Li ion battery cathodes. Compounds such as Li[Ni_1/3Co_1/3Mn_1/3]O₂ (often called NMCs) are currently being commercialized for use in consumer electronic batteries, but the high cobalt content makes them too expensive for vehicular applications such as electric vehicles (EV), plug-in hybrid electric vehicles (PHEVs), or hybrid electric vehicles (HEVs). To reduce materials costs, we have explored partial or full substitution of Co with Al, Ti, and Fe. Fe substitution generally decreases capacity and results in poorer rate and cycling behavior. Interestingly, low levels of substitution with Al or Ti improve aspects of performance with minimal impact on energy densities, for some formulations. High levels of Al substitution compromise specific capacity, however, so further improvements require that the Ni and Mn content be increased and Co correspondingly decreased. Low levels of Al or Ti substitution can then be used offset negative effects induced by the higher Ni content. The structural and electrochemical characterization of substituted NMCs is presented in this paper.

High-power and high-energy lithium-ion cells are being studied at Argonne National Laboratory (Argonne) as part of the U.S. Department of Energy's FreedomCar and Vehicle Technologies (FCVT) program. Cells ranging in capacity from 1 mAh to 1Ah, and containing a variety of electrodes and electrolytes, are examined to determine suitable material combinations that will meet and exceed the FCVT performance, cost, and safety targets. In this article, accelerated aging of 18650-type cells, and characterization of components harvested from these cells, is described. Several techniques that include electrochemical measurements, analytical electron microscopy, and x-ray spectroscopy were used to study the various cell components. Data from these studies were used to identify the most likely contributors to property degradation and determine mechanisms responsible for cell capacity fade and impedance rise.

Reducing battery materials to nano-scale dimensions may improve battery performance while maintaining the use of low-cost materials. However, we need better characterization tools with atomic to nano-scale resolution in order to understand degradation mechanisms and the structural and mechanical changes that occur in these new materials during battery cycling. To meet this need, we have developed a micro-electromechanical systems (MEMS)-based platform for performing electrochemical measurements using volatile electrolytes inside a transmission electron microscope (TEM). This platform uses flip-chip assembly with special alignment features and multiple buried electrode configurations. In addition to this platform, we have developed an unsealed platform that permits in situ TEM electrochemistry using ionic liquid electrolytes. As a test of these platform concepts, we have assembled MnO₂ nanowires on to the platform using dielectrophoresis and have examined their electrical and structural changes as a function of lithiation. These results reveal a large irreversible drop in electronic conductance and the creation of a high degree of lattice disorder following lithiation of the nanowires. From these initial results, we conclude that the future full development of in situ TEM characterization tools will enable important mechanistic understanding of Li-ion battery materials.

For over 10 years Sandia Labs have been involved in an US DOE-funded program aimed at developing electric vehicle batteries for transportation applications. Currently this program is called "Advanced Battery Research (ABR)." In this effort we were preparing 18650 cells with electrodes supplied by or purchased from private companies for thermal abuse and electrical characterization studies. Lately, we are coating our own electrodes, building cells and evaluating performance. This paper describes our extensive in-house facilities for slurry making, electrode coating, cell winding etc. In addition, facilities for electrical testing and thermal abuse will be described. This facility allows us to readjust our focus quickly to the changing demands of the still evolving ABR program. Additionally, we continue to make cells for our internal use. We made several 18650 cells both primary (Li-CFx) and secondary (Li-ion) and evaluated performance. For example Li-CF_x cells gave ~2.9Ahr capacity at room temperature. Our high voltage Li-ion cells consisting of carbon anode and cathode based on LiNi _0.4Mn _0.3Co _0.3O₂ in organic electrolytes exhibited reproducible behavior and gave capacity on the order of 1Ahr. Performance of Li-ion cells at different temperatures and thermal abuse characteristics will be presented.

Ionic liquid has been utilized as safe electrolyte solution for lithium-ion batteries. Reversible charge / discharge cycling of the graphite electrode in the ionic liquid has been achieved with polyacrylic acid polymer binder, which can suppress the organic cation intercalation to the graphite. Cycleability of the graphite-silicon composite electrodes prepared with polyacrylate binder was significantly improved in comparison to the conventional PVdF binder, and it has been demonstrated that the reversible cycling with 1000 mAh g^-1 for 30 cycling test is possible in ionic liquid. The possibility of the safe and high-energy lithium-ion battery is discussed through the preliminary study on Li₂MnO₃-LiCo_1/3Ni_1/3Mn_1/3O₂ based positive electrode and graphite-silicon-polyacrylate composite negative electrode with the ionic liquid electrolyte.

Several different cathode materials for Li-ion batteries with a general formula Li₂MXO₄ (M= Fe, Mn, Ni, V and X= Si, Ti) were synthesized and characterized. Generally those materials can be classified into the group of silicates with tetrahedral coordinated cations and into titanates with a rock-salt structure. The common characteristic of these two families of new cathode materials is two lithium cations in the structure and at lest theoretical possibility to exchange more than one electron per transition metal and consequently enable much higher specific capacity of battery. Detailed structural and electrochemical characterization (including some in-situ characterization techniques, like X-ray absorption and Mössbauer spectroscopy) are discussed in this paper. Influence of the structural stability and particle size is discussed based on the obtained electrochemical results. Finally we show for the first time operation of Li₂FeSiO₄ with graphite electrode at 60°C.

Advances in lithium primary battery technology, which serves as the gold standard power source for the dismounted soldier, have not kept pace with the ever increasing power and energy requirements of modern military electronic equipment. Fuel cells have long been touted as the solution to the dismounted soldier's power and energy problems, but until recently, have largely failed to live up to that promise. There is still a pressing need for better power sources at the Watt or sub-Watt level, especially in applications requiring nontraditional form factors (thin, prismatic) or those having special requirements like flexibility or conformability, where existing battery technology falls short. To address these needs, Honeywell is developing a Self Regulating Fiber Fuel Cell, which utilizes a novel fuel chemistry and regulation mechanism and micro fabrication techniques to create a flexible, conformal power source with substantially better energy density and specific energy compared to state of the art lithium primary batteries. This paper will cover Honeywell's progress on the Fiber Fuel Cell Project.

Solar energy is the only renewable energy source that could largely replace the burning of fossil fuels and is the most rapidly deployable energy source, but because of its high cost, makes up only 1% of the world's energy production. Concentrated photovoltaics (CPV) requires the least land and by far the least semiconductor material of any photovoltaic technology, but is the most expensive. Its high cost arises from the need to approximately lattice match the substrate and III-V materials in the three-junction CPV solar cells to maximize minority-carrier recombination times and hence cell efficiencies. Lattice-matching forces the use of Ge substrates, which are very expensive and fragile, making the cells very expensive. We give experimental evidence and theoretical arguments that, unlike III-V cells, CdTe-based multijunction cells need not be lattice-matched and could be grown on Si by high-throughput molecular beam epitaxy, reducing the cost an order of magnitude. That would allow the use of much lower solar concentrations, greatly reducing the tracking and optics costs. Also, efficiency calculations, assuming lattice matching not to be required for II-VI materials, indicate that the highest-efficiency three-junction II-VI cells should have efficiencies 3-8% (absolute) higher than those of the highest-efficiency three-junction III-V cells. We have fabricated and tested single-junction and twojunction CdZnTe/Si solar cells, concentrating on the value of the open-circuit voltage Voc because it measures the absorber-material limitations on cell efficiencies. We found V_oc ≥ 90% of its thermodynamic limit, equivalent to the best reported results for single-junction III-V cells.

Higher efficiency solar cells are required to reduce solar array mass, stowed volume, and cost for numerous commercial and military applications. Conventional solar cell made of thin-film or crystal-Si (c-Si) or other thin films have limited conversion efficiency of 10 to 20% with the cost of $3-$5/Wp. Current state-of-the-art crystalline multijunction solar cells are ~30 % efficient with the cost of $30 to $40 /Wp. Increasing conversion efficiency of > 30% will enable to reduce the cost < $1/Wp and useful for various power platforms supporting mobile wireless, laptop, tent applications. Solar cell comprises with three dimensional blocks are shown to be higher conversion-efficiency than standard flat-type solar cell. Incorporating nano-scaled blocks in solar cell structures are shown to be increased performances due to (i) increase of the surface area to volume ratio, (ii) brining the junction closer to the carrier generation region which eliminate the carrier recombination , (iii) absorption of all incident photon flux, and (iv) broadening the absorption spectrum. Our activities on next generation high performance solar cells based on micro-nano scaled structures and various material systems will be presented. Details fabrication process of micro-nano scaled solar cell friendly to mass scale manufacturing will be also be described. We have achieved more than 20x optical performance enhancement for the solar cell based on micro-scaled structures, than that of flat-type (standard) solar cell, fabricated on the same Si substrate and same process. Simulation results showed that significant improvement in conversion efficiency more than 30% is possible for even c-Si solar cell based on the micro-nano scaled structures. Key issues and challenges for bringing it to the manufacturing will be discussed.

Quantum-well based solar cells have the potential to deliver ultra-high efficiencies in single-junction devices, efficiencies that in theory can approach 45% in un-concentrated sunlight over a wide range of environmental conditions. In this work, thin-film GaAs-based quantum well solar cells are demonstrated that operate at voltages higher than previous state-of-the-art GaAs devices. Higher open circuit voltages result from the use of a novel structure incorporating a wide band gap barrier layer within a heterojunction depletion region. Ultra-low dark current is observed from this structure as result of the simultaneous reduction of carrier diffusion and space charge recombination. Efficient carrier extraction of photogenerated carries over the potential barriers within the structure is achieved by increasing the field strength and tailoring the barrier profile to enhance thermionic emission and tunneling. High open circuit voltages (>1.1 V @ 25 A/cm²) and fill factors (> 80%) are demonstrated in multi-layer depletion region structures incorporating both an extended region of wide band gap material and an InGaAs quantum well within a GaAs base layer. These ground breaking results indicate that it is possible to simultaneously increase both the current and voltage output of GaAs-based solar cells.

Nitride semiconductors possess a number of unique material properties applicable to energy harvesting photovoltaic devices, including a large range of energy gaps, superior radiation resistance, and tolerance to high temperatures. We present here our experimental results related to the self-assembled InN quantum dots formed on Si substrates. We have been successful at synthesizing InN quantum dots using the metal-organic chemical vapor deposition (MOCVD) process. We demonstrate the synthesis of a high density of InN dots exhibiting excellent structural and optical properties. An unprecedented range of absorption energies, ranging from the infrared to the ultraviolet, can be obtained by embedding InN-based quantum dots in a wide band gap GaN barrier. The combination of energy-gaps accessible to III-V nitride materials may be used to reap the benefits of advance quantum dot device concepts involving hot carrier effects or multiple carrier generation processes.

The advantages of thermoelectric energy conversion technologies are briefly summarized. Recent material advances are discussed, with the focus on one-dimensional (1-D) self-assembled molecular materials as building blocks for new thermoelectric materials. The preparation, doping, and thermal characterization of phthalocyanine based materials are presented. The thermal conductivity of the doped material is lower than the undoped material even though the electrical conductivity of the doped material is orders of magnitude higher than the undoped material. This is counter intuitive against the backdrop of the Wiedemann-Franz treatment of thermal conductivity in electrical conductors from which one would expect thermal and electrical conductivity to both increase with introduction of additional charge carriers. These unusual results can be understood as a competition between the generation of an increased number of charge carriers and enhanced phonon scattering resulting from the introduction of chemical dopants. The thermal conductivity of the undoped phthalocyanines has been found to be small and only modestly temperature dependent in the 50-300 C range, but it is larger than a previous, indirect measurement.

In this paper, deposition of CdS thin films by thermal evaporation was made using high purity CdS powders as the source material. It is found that the electrical conductivity of thermal evaporated CdS thin films is very sensitive to heat. The change of surface temperature of this material leads to the significant increase in its electrical conductivity as shown by the relationship of temperature and electrical resistance. It is concluded that such a temperature-sensitive conductive behavior comes from the thermally-activated electron ejection in CdS.

Efficiency of thermoelectric materials is generally discussed in terms of the dimensionless figure-of-merit, ZT = S²σT/κ, Many researchers have found that it is possible to reduce the lattice thermal conductivity by incorporating nanostructures (i.e. nanoparticles or heterobarriers) into materials, thereby scattering phonons. At the same time, it has been theoretically predicted and experimentally demonstrated that barriers can be used to "filter" the distribution of carriers which contribute to conduction. By doing so, it is possible to significantly increase the Seebeck coefficient while only modestly decreasing the electrical conductivity. As a result of this energy-dependent scattering of carriers, the thermoelectric power factor is increased. We present theoretical and experimental results for metal/semiconductor nanocomposites consisting of metallic rareearth- group V nanoparticles within III-V semiconductors (e.g. ErAs:InGaAlAs) demonstrating both an increase in thermoelectric power factor and a decrease in thermal conductivity, resulting in a large figure of merit. We also discuss metal/semiconductor superlattices made of lattice-matched nitride materials for electron filtering and the prospects of these materials for efficient thermoelectrics, especially at high temperatures. Finally, we will discuss both various synthesis techniques for these materials, including the prospects for bulk growth, and also devices fabricated from these materials.

There is increasing need for self-sufficient power sources for wireless sensors and electronics that can extend device performance beyond what is available from conventional batteries. Thermoelectric approaches for developing such power sources using geothermal and body heat are attractive. RTI has developed a prototype "thermal ground stake" wireless sensor node powered by thermoelectric (TE) energy harvesting that lends itself to unattended ground sensors for covert military and intelligence operations where TE powered sensors are concealed in the ground. In another application, RTI International and QUASAR are jointly developing an integrated body-worn biosensor system powered by body heat thermoelectric energy harvesting.

Thermoelectric energy harvesting has increasingly gained acceptance as a potential power source that can be used for numerous commercial and military applications. However, power electronic designers have struggled to incorporate energy harvesting methods into their designs due to the relatively small voltage levels available from many harvesting device technologies. In order to bridge this gap, an ultra-low input voltage power conversion method is needed to convert small amounts of scavenged energy into a usable form of electricity. Such a method would be an enabler for new and improved medical devices, sensor systems, and other portable electronic products. This paper addresses the technical challenges involved in ultra-low-voltage power conversion by providing a solution utilizing novel power conversion techniques and applied technologies. Our solution utilizes intelligent power management techniques to control unknown startup conditions. The load and supply management functionality is also controlled in a deterministic manner. The DC to DC converter input operating voltage is 20mV with a conversion efficiency of 90% or more. The output voltage is stored into a storage device such as an ultra-capacitor or lithium-ion battery for use during brown-out or unfavorable harvesting conditions. Applications requiring modular, low power, extended maintenance cycles, such as wireless instrumentation would significantly benefit from the novel power conversion and harvesting techniques outlined in this paper.

Harvesting energy from ambient vibration is a promising method for providing a continuous source of power for wireless sensor nodes. However, traditional energy harvesters are often derived from resonant linear oscillators which are capable of providing sufficient output power only if the dominant frequency of input vibrations closely matches the device resonant frequency. The limited scope of such devices has sparked an interest in the use of nonlinear oscillators as mechanisms for broadband energy harvesting. In this study, we investigate the harvesting performance of an electromagnetic harvester sustaining oscillations through the phenomena of magnetic levitation. The nonlinear behavior of the device is effectively modeled by Duffing's equation, and direct numerical integration confirms the broadband frequency response of the nonlinear harvester. The nonlinear harvester's power generation capabilities are directly compared to a linear electromagnetic harvester with similar dynamic parameters. Experimental testing shows that the presence of both high and low amplitude solutions for the nonlinear energy harvester results in a tendency for the oscillator to remain in a low energy state for non-harmonic vibration inputs, unless continuous energy impulses are provided. We conclude by considering future applications and improvements for such nonlinear devices.

Fuel-based portable power systems, including combustion and fuel cell systems, take advantage of the 80x higher energy density of fuel over lithium battery technologies and offer the potential for much higher energy density power sources - especially for long-duration applications, such as unattended sensors. Miniaturization of fuel-based systems poses significant challenges, including processing of fuel in small channels, catalyst poisoning, and coke and soot formation. Recent advances in micro-miniature combustors in the 200Watt thermal range have enabled the development of small power sources that use the chemical energy of heavy fuel to drive thermal-to-electric converters for portable applications. CUBE Technology has developed compact Micro-Furnace combustors that efficiently deliver high-quality heat to optimized thermal-to-electric power converters, such as advanced thermoelectric power modules and Stirling motors, for portable power generation at the 10-50Watt scale. Key innovations include a compact gas-gas recuperator, innovative heavy fuel processing, coke- & soot-free operation, and combustor optimization for low balance-of-plant power use while operating at full throttle. This combustor enables the development of robust, high energy density, miniature power sources for portable applications.

Crystalline TiO₂ film was formed on PET(polyethlene terephthalate) film by radio frequency sputter deposition method using a sintered TiO₂ target by adding H₂O gas to Ar gas for sputtering. X-ray diffraction analysis revealed that the crystal structure of the film of 100 nm thick was confirmed to be anatase crystallites of TiO₂. In order to elucidate the mechanism of low temperature crystallization thus observed, direct measurement of surface temperature of growing films during sputter deposition was carried out by two methods of an infrared thermometer from the outside of vacuum chamber and a thermocouple attached to the growing film surface. Upon the beginning of sputter deposition in Ar gas, film temperature increased rapidly and became constant at 120°C after 30 min. Addition of H₂O gas to Ar gas for sputtering resulted in further increase in film temperature and reached to 230 °C depending on the deposition conditions. Furthermore, photocatalytic performance of decomposition of methylene blue was examined to be enhanced remarkably as a result of crystallization of the film. It was concluded that low temperature crystallization of TiO₂ film by sputter deposition was explained in terms of local heating of thin shallow surface region of growing film by kinetic energy deposition of sputtered particles.

Zinc nitride and zinc oxide can have wide range applications owing to their band-gap changes and controlling capability of n-type to p-type behavior by impurity doping. Thus, zinc oxy-nitrides can be utilized to design novel photonic devices such as solar cells, UV-Visible devices, and light emitting diodes. In this paper, feasibility of tuning the optical and electronic properties of zinc oxynitride thin films in an rf magnetron sputtering deposition. It was found that the change of gas composition such as Ar: N₂: O₂ can change the properties of zinc nitride films for a wide range. The absorption coefficient of zinc nitride films were larger than zinc oxide thin films in low photon energy range, in particular visible region of the spectrum. These results indicated that the zinc nitride may find suitable applications in solar cells and photonic devices.

We report a simple sonochemical method for the seeding and synthesis of Zinc Oxide nanowire arrays that can be formed on a number of substrates that are stable in alcohol and aqueous solution. Vertically aligned ZnO NWs were synthesized from a single solution at room-ambient via ultrasonic excitation. Prior to the NW growth, a ZnO seed layer was deposited using the same system with a different solution. The optimal conditions to produce a high density of oriented wires along with their optical characteristics are presented for ZnO NWs with a significantly high growth rate compared with traditional growth techniques such as evaporation, chemical vapor deposition and sputtering. Our method promises a mass-manufacturable process for fast and inexpensive ZnO NW production for practical low cost electronics, photonics and energy conversion applications.

In this paper, we demonstrate an approach to simultaneously transfer single crystal devices in the shape of vertically oriented 1-D silicon micropillars, while establishing a direct electrical and mechanical connection to a target surface of any topology using an innovative harvest/lift-off process coupled with a conducting thermoplastic composing of polyaniline (PAni) and polymethylmethacrylate (PMMA) composite. The mixture acts as a stable anchoring layer and as a conducting layer for the bottom electrode. The insulating layer comprised of PMMA while the top electrode can be formed by evaporating thin metal films.

In many commercial, industrial, and military applications, supplying power to electronics through a thick metallic barrier without compromising its structural integrity would provide tremendous advantages over many existing barrier-penetrating techniques. The Faraday shielding presented by thick metallic barriers prevents the use of electromagnetic power-transmission techniques. This work describes the electrical optimization of continuouswave power delivery through thick steel barriers using ultrasound. Ultrasonic channels are formed by attaching pairs of coaxially-aligned piezoelectric transducers to opposite sides of thick steel blocks. The thickness of the steel considered is on the order of, or greater than, one quarter wavelength of the acoustic power signal inside of steel, requiring the use of wave propagation theory to properly analyze the system. A characterization and optimization methodology is presented which measures the linear two-port electrical scattering parameters of the transducersteel- transducer channel. Using these measurements, the simultaneous conjugate impedance-matching conditions at both transducers are calculated, and electrical matching-networks are designed to optimize the power transfer from a 50Ω power amplifier on one side of the steel block to a 50Ω load on the opposite side. In addition, the impacts of, and interactions between, transducer and steel geometries are discussed, and some general guidelines for selecting their relationships are presented. Measurements of optimized systems using transducers designed to resonate at 1 MHz with diameters from 12.7 mm to 66.7 mm, and steel block thicknesses from 9.5 mm to 63.5 mm, reveal power transfer efficiencies as high as 55%, and linear delivery of 81 watts through an optimized channel.

Solar energy conversion concept based on nanostructured materials has attracted much attention as an avenue to develop cheaper and more efficient solar cells. Both dye molecules and quantum dots can sensitize high band gap semiconductor by injecting carriers to the conduction band (CB) or valence band (VB) of the high band gap material, if energy band levels are in appropriate configuration and have a suitable bond between them. However, other physical properties of dye anchored and quantum dot embedded nanostructured semiconductor films offers the possibility of designing hybrid systems of higher efficiency. The low efficiency of dye-sensitized solar cells is partly attributed to the poor electron transport properties of the dye coated nanocrystalline matrix. Encapsulation of PbS quantum dots could enhance the electronic conductivity of nanostructured ZnO films. PbS quantum dot sensitized ZnO films shows sensitizing response to light absorption in ZnO, PbS QDs and dyes anchored to ZnO. As a result of the improvement of transport properties by the QDs, photocurrent response of composite system due to light absorption by ZnO and dye are also enhanced. Possibilities of adopting this concept in solar cells and multi-band photon detectors will be discussed.

This paper describes hierarchically architectured development of an energy harvesting (EH) system that consists of micro and/or macro-scale harvesters matched to multiple components of remote wireless sensor and communication nodes. The micro-scale harvesters consist of thin-film MEMS piezoelectric cantilever arrays and power generation modules in IC-like form to allow efficient EH from vibrations. The design uses new high conversion efficiency thin-film processes combined with novel cantilever structures tuned to multiple resonant frequencies as broadband arrays. The macro-scale harvesters are used to power the collector nodes that have higher power specifications. These bulk harvesters can be integrated with efficient adaptive power management circuits that match transducer impedance and maximize power harvested from multiple scavenging sources with very low intrinsic power consumption. Texas MicroPower, Inc. is developing process based on a composition that has the highest reported energy density as compared to other commercially available bulk PZT-based sensor/actuator ceramic materials and extending it to thin-film materials and miniature conversion transducer structures. The multiform factor harvesters can be deployed for several military and commercial applications such as underground unattended sensors, sensors in oil rigs, structural health monitoring, supply chain management, and battlefield applications such as sensors on soldier apparel, equipment, and wearable electronics.