This PDF file contains the front matter associated with SPIE Proceedings Volume 9083, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.

Carbon-based nanostructures have been the center of intense research and development for more than two decades now. Of these materials, graphene, a two-dimensional (2D) layered material system, has had a significant impact on science and technology over the past decade after monolayers of this material were experimentally isolated in 2004. The recent emergence of other classes of 2D graphene-like layered materials has added yet more exciting dimensions for research in exploring the diverse properties and applications arising from these 2D material systems. For example, hexagonal-BN, a layered material closest in structure to graphene, is an insulator, while NbSe₂, a transition metal di-chalcogenide, is metallic and monolayers of other transition metal di-chalcogenides such as MoS₂ are direct band-gap semiconductors. The rich spectrum of properties that 2D layered material systems offer can potentially be engineered ondemand, and creates exciting prospects for using such materials in applications ranging from electronics, sensing, photonics, energy harvesting and flexible electronics over the coming years.

Layered two-dimensional (2D) semiconductors beyond graphene have been emerging as potential building blocks for the next-generation electronic/photonic applications. Representative metal chalcogenides, including the widely studied MoS2, possess similar layered crystal structures with weak interaction between adjacent layers, thus allowing the formation of stable thin-layer crystals with thickness down to a few or even single atomic layer. Other important chalcogenides, involving earth-abundant and environment-friendly materials desirable for sustainable applications, include SnS2 (band gap: 2.1 eV) and SnS (band gap: 1.1 eV). So far, commonly adopted for research purpose are mechanical and liquid exfoliation methods for creating thin layers of such 2D semiconductors. Most recently, chemical vapor deposition (CVD) was attracting significant attention as a practical method for producing thin films or crystal grains of MoS₂. However, critical yet still absent is an effective experimental approach for controlling the positions of thin crystal grains of layered 2D semiconductors during the CVD process. Here we report the controlled CVD synthesis of thin crystal arrays of representative layered semiconductors (including SnS₂ and SnS) at designed locations on chip, promising large-scale optoelectronic applications. Our work opens a window for future practical applications of layered 2D semiconductors in integrated nano-electronic/photonic systems.

In this paper, we first review the impressive properties of two-dimensional (2D) nanocrystals, primarily graphene and beyond-graphene 2D crystals, such as transition-metal dichalcogenides (TMDs), and then highlight some applications uniquely enabled by these materials for designing next-generation low-power and low-loss “green electronics”. Key challenges of 2D crystals relevant to such applications are discussed as well.

This paper reviews our recent results of high-field electrical and thermal properties of atomically thin two-dimensional materials. We show how self-heating affects velocity saturation in suspended and supported graphene. We also demonstrate that multi-valley transport must be taken into account to describe high-field transport in MoS₂. At the same time we characterized thermal properties of suspended and nanoscale graphene samples over a wide range of temperatures. We uncovered the effects of edge scattering and grain boundaries on thermal transport in graphene, and showed how the thermal conductivity varies between diffusive and ballistic heat flow limits.

We have developed a theory for the generation and detection of coherent phonons in carbon based nanotstructures such as single walled nanotubes (SWNTs), graphene, and graphene nanoribbons. Coherent phonons are generated via the deformation potential electron/hole-phonon interaction with ultrafast photo-excited carriers. They modulate the reflectance or absorption of an optical probe pules on a THz time scale and might be useful for optical modulators. In our theory the electronic states are treated in a third nearest neighbor extended tight binding formalism which gives a good description of the states over the entire Brillouin zone while the phonon states are treated using valence force field models which include bond stretching, in-plane and out-of-plane bond bending, and bond twisting interactions up to fourth neighbor distances. We compare our theory to experiments for the low frequency radial breathing mode (RBM) in micelle suspended single-walled nanotubes (SWNTs). The analysis of such data provides a wealth of information on the dynamics and interplay of photons, phonons and electrons in these carbon based nanostructures.

Among different carbon materials (diamond, graphite, fullerene, carbon nanotubes), graphene and more complex graphene-based structures attracted a considerable attention. The gapless energy spectrum of graphene implies that graphene can absorb and emit photons with rather low energies corresponding to terahertz (THz) and infrared (IR) ranges of the electromagnetic spectrum. In this presentation, the discussion is focused on the double-graphene-layer (double-GL) structures. In these structures, GLs are separated by a barrier layer (Boron Nitride, Silicon Carbide, and so on). Applying voltage between GLs, one can realize the situation when one GL is filled with electrons while the other is filled with holes. The variation of the applied voltage leads to the variations of the Fermi energies and, hence, to the change of the interband and intraband absorption of electromagnetic radiation and to the variation of the tunneling current. The plasma oscillations in double-GL structures exhibit interesting features. This is mainly because each GL serves as the gate for the other GL. The spectrum of the plasma oscillations in the double-GL structures falls into the terahertz range (THz) of frequencies and can be effectively controlled by the bias voltage. In this paper, we discuss the effects of the excitation of the plasma oscillations by incoming THz radiation and by optical radiation of two lasers with close frequencies as well as negative differential conductivity of the N-type and Z-type. These effects can be used in resonant THz detectors and THz photomixers. The models of devices based on double-GL structures as well as their characteristics are discussed.

In the present paper we review some of the present technologies of interest for terahertz (THz) applications, and the physics and modeling of ultra-high frequency devices such as high electron mobility transistors (HEMTs) which have achieved THz frequencies. We present results of full band Cellular Monte Carlo (CMC) physics based simulation of InP and GaN based HEMTs of current interest to industry, and in particular, we address the current limitations in their frequency response in terms of the material and device structure, and the ultimate limits of scaling for such technologies.

There has been a continued interest in the terahertz (THz) imaging due to penetration and non-ionizing properties. Realtime imaging in this spectral range has been demonstrated using infrared microbolometer technology with external illumination by quantum cascade lasers (QCL). However, to achieve high sensitivity, it is necessary to develop focal plane arrays using enhanced THz-absorbing materials. One attractive option to achieve real time THz imaging is MEMS bi-material sensor with embedded metamaterial absorbers, consisting of a periodic array of metallic squared elements separated from a homogeneous metallic ground plane by a dielectric layer. We have demonstrated that the metamaterial films can be designed using standard MEMS materials such as silicon oxide (SiO_x), silicon oxinitrate (SiO_xN_y) and aluminum (Al), to achieve nearly 100 % resonant absorption matched to the illumination source, while providing structural support, desired thermomechanical properties and access to external optical readout. The metamaterial structure absorbs the incident THz radiation and transfers the heat to bi-material microcantilevers that are connected to the substrate, which acts as a heat sink, via thermal insulating legs. A temperature gradient builds up in the legs, allowing the overall structure to deform proportionally to the absorbed power. The amount of deformation can be probed by measuring the displacement of a laser beam reflected from the sensor’s metallic ground plane. Several sensor configurations have been designed, fabricated and characterized to optimize responsivity, speed of operation and minimize structural residual stress. Measured figures of merit indicate that the THz MEMS sensors have a great potential for real-time imaging.

Metal free direct growth of graphene on h-BN using a high temperature (~1550°C) chemical vapor deposition technique was done under Ar environment. Growth temperature, methane partial pressure, hydrogen/methane flow ratio, and growth time were varied and optimized. Raman spectroscopy clearly showed the signature of graphene with G- (~1580cm^-1) and 2D-mode (~2700cm^-1). The smallest width of G- and 2D-peak was 30 and 55cm^-1, respectively, and the Raman I_2D/I_G ratio varied between 0.7 and 1.8. Raman D-peak (~1350cm^-1) shows a strong dependence on growth temperature with the smallest I_D/I_G value of 0.15 at 1550°C. In the case of long growth, nitrogen and boron doping were detected by x-ray photoelectron spectroscopy with a small Raman D’-peak. A continuous graphene film with the rms roughness (1×1 μm² area) of 0.32nm was shown by atomic force microscopy. Early stage of growth revealed circular shaped nucleation islands, the density and heights of which are ~15/μm² and 1-2 graphene monolayer (ML), respectively. The hydrogen/methane flow ratio was found to be a critical parameter to obtain smooth 2D growth. Growth of h-BN is performed with ammonia borane, hydrogen and Ar. The growth is found to be critically dependent on the conditions of the ammonia boran precursor. Reproducible continuous films of h-BN are reported.

Antennas collect radio waves and channel them into radio frequency (RF) transmission lines which direct the signals to circuits from which information can be demodulated and decoded. Glass, the most common portal between outside and inside environments, is clear at the visible part of the electromagnetic spectrum, and it is also relatively transparent to a large portion of the electromagnetic spectrum useful for radio wave communications. Since glass as a building material is used everywhere, it could be a readily accessible substrate upon which to mount or fabricate the antennas and RF electronics, but only if these circuit components are also transparent. In this paper, we present our development to date of glass RF circuits along two tracks: 1) transparent antennas and 2) graphene based active and passive circuit elements. Along the first track we have demonstrated antennas made from nanowire films capable of an optical transparency of 72% and sheet resistance of 4-5Ω/sq. Along the second track, we have in so far demonstrated graphene on glass field effect transistors with an fmax of 7 GHz, varactors with 1.4:1 tuning range, resistors with 3-70 kΩ, and capacitors from 13-860 pF. This is just the start; our plans are to increase the frequency and tuning ranges of the active and passive devices. Since graphene is inherently transparent at visible wavelengths, we ultimately would like to merge these two tracks to integrate active and passive RF circuitry with the antenna either directly on glass or as an applique put on glass, circuits which we’ve termed RF Glass®.

Evolution in transistor technology from increasingly large power consuming single gate planar devices to energy efficient multiple gate non-planar ultra-narrow (< 20 nm) fins has enhanced the scaling trend to facilitate doubling performance. However, this performance gain happens at the expense of arraying multiple devices (fins) per operation bit, due to their ultra-narrow dimensions (width) originated limited number of charges to induce appreciable amount of drive current. Additionally arraying degrades device off-state leakage and increases short channel characteristics, resulting in reduced chip level energy-efficiency. In this paper, a novel nanotube device (NTFET) topology based on conventional group IV (Si, SiGe) channel materials is discussed. This device utilizes a core/shell dual gate strategy to capitalize on the volume-inversion properties of an ultra-thin (< 10 nm) group IV nanotube channel to minimize leakage and short channel effects while maximizing performance in an area-efficient manner. It is also shown that the NTFET is capable of providing a higher output drive performance per unit chip area than an array of gate-all-around nanowires, while maintaining the leakage and short channel characteristics similar to that of a single gate-all-around nanowire, the latter being the most superior in terms of electrostatic gate control. In the age of big data and the multitude of devices contributing to the internet of things, the NTFET offers a new transistor topology alternative with maximum benefits from performance-energy efficiency-functionality perspective.

Single-walled carbon nanotubes (SWNT) could replace silicon in high-performance electronics with their exceptional electrical properties and intrinsic ultra-thin body. During the past five years, the major focus of this field is gradually shifting from proof-of-concept prototyping in academia to technology development in industry with emphasis on manufacturability and integration issues. Here we will review some most significant recent advances, with focus on assembling high purity semiconducting SWNTs into well aligned arrays. Future challenges and research opportunities in this field will also be discussed.

This paper provides an overview of research at the Adaptive Optics Center of Excellence for national security (AOCoE) at the Naval Postgraduate School (NPS). The Center was established in 2011 with the sponsorship of the Office of Naval Research, National Reconnaissance Office, and Air Force research Laboratory. Research is in two areas: Segmented Mirror telescope (SMT) for imaging satellites and High Energy Laser Beam Control. SMT consists of a 3 meter diameter telescope with six segments and each segment has actuators for surface control and segment alignment. SMT research areas include developing improved techniques for surface control and segment alignment, and reduction in segment vibration by using tuned mass dampers. Research is also performed in adding a deformable mirror into the SMT optical path to correct for residual beam aberration not corrected by the primary mirror actuators. For high energy laser beam control the research areas are acquisition, tracking, and pointing, optical beam jitter control, and application of adaptive optics for correcting beam aberration due to air turbulence. The current focus is on adaptive optics for deep turbulence.

Efficient propagation of light through the atmosphere requires the compensation of phase distortions induced by the atmosphere, thermal lensing, thermal blooming, or aero-optics. We have developed a deformable mirror engineered to compensate these aberrations while reflecting high power radiation with minimal heating and thermally induced distortion. We present the results of a multi-year effort to address many of the challenges with existing state-of-the-art designs while reducing cost, complexity, and manufacturing time.

We demonstrate feasibility of a an spatially-modulated multi-photon microscopy (S-MPM) technique that can image through complex media that strongly scatters light, and we describe performance achieved with a prototype instrument. S-MPM’s imaging advantages are enabled by a high-speed, microelectromechanical spatial light modulator (MEMS SLM) subsystem with 1020 independently controllable mirror segments.

The use of Adaptive Optics (AO) to correct for aberrations in a wavefront of propagating light has become customary for Astronomical applications and is now expanding to many other areas going from medical imaging to industrial applications. However, the propagation of light underwater has remained out of the main stream AO community for a variety of reasons, not least the shear difficulty of the situation. Our group has become a program that attempts to define under which circumstances such a correction could be envisioned. We take advantage of the NRL laboratory facility in Stennis, MS, where a large Plexiglas tank of water is equipped with heating and cooling plates that allow for a well measured thermal gradient that in turn generates different degrees of turbulence that can distort a propagating laser beam. In this paper we report on the preliminary findings of this ongoing program. The paper will describe the facility and the AO test-bed, the measurements made and some of the preliminary result.

A prototype in-situ laser-absorption sensor for the real-time composition measurement (CO, CH₄, H₂O and CO₂) of synthesis gas products of coal gasification (called here syngas) was designed, tested in the laboratory, and demonstrated during field-measurement campaigns in a pilot-scale entrained flow gasifier at the University of Utah and in an engineering-scale, fluidized-bed transport gasifier at the National Carbon Capture Center (NCCC). The prototype design and operation were improved by the lessons learned from each field test. Laser-absorption measurements are problematic in syngas flows because efficient gasifiers operate at elevated pressures (10-50 atm) where absorption transitions are collision broadened and absorption transitions that are isolated at 1 atm become blended into complex features, and because syngas product streams can contain significant particulate, producing significant non-absorption scattering losses of the transmission of laser light. Thus, the prototype sensor used a new wavelength-scanned, wavelength-modulation spectroscopy strategy with 2f-detection and 1f-normalization (WMS-2f/1f) that can provide sensitive absorption measurements of species with spectra blended by collision broadening even in the presence of large non-absorption laser transmission losses (e.g., particulate scattering, beam steering, etc.). The design of the sensor for detection of CO, CH₄, H₂O and CO₂ was optimized for the specific application of syngas monitoring at the output of large-scale gasifiers. Sensor strategies, results and lessons learned from these field measurement campaigns are discussed.

Opportunities exist to improve on-line process control in energy applications with a fast, non-destructive measurement of gas composition. Here, we demonstrate a Raman sensing system which is capable of reporting the concentrations of numerous species simultaneously with sub-percent accuracy and sampling times below one-second for process control applications in energy or chemical production. The sensor is based upon a hollow-core capillary waveguide with a 300 micron bore with reflective thin-film metal and dielectric linings. The effect of using such a waveguide in a Raman process is to integrate Raman photons along the length of the sample-filled waveguide, thus permitting the acquisition of very large Raman signals for low-density gases in a short time. The resultant integrated Raman signals can then be used for quick and accurate analysis of a gaseous mixture. The sensor is currently being tested for energy applications such as coal gasification, turbine control, well-head monitoring for exploration or production, and non-conventional gas utilization. In conjunction with an ongoing commercialization effort, the researchers have recently completed two prototype instruments suitable for hazardous area operation and testing. Here, we report pre-commercialization testing of those field prototypes for control applications in gasification or similar processes. Results will be discussed with respect to accuracy, calibration requirements, gas sampling techniques, and possible control strategies of industrial significance.

Fiber Fabry-Perot (FP) interferometry is one of the most important tools for harsh environment sensing because of its great flexibility of sensor material selection, superior long-­‐term stability, and nature of remote passive operation. Virginia Tech’s Center for Photonics Technology has been involved in the research of this field for many years. After a quick review of the typical methods for the construction of F-P sensors, emphasis will be placed on the whitelight interferometry, which is perhaps the most robust interferometric sensor demodulation technique today. The recent discovery of an additional phase will be presented and its significance to the sensor demodulation will be discussed.

Chemical gas sensors can have an enormous impact on optimizing complex processes as well as facilitate disease diagnosis. In this article, we demonstrate how sensing of gas molecules is influencing the next generation of engines for transportation applications, as well as in disease diagnosis. In such applications, the demands on sensors are quite extreme. Not only does the device have to detect the gas of interest with high sensitivity, it also has to discriminate against other species present in a complex environment, such as combustion exhaust and human breath. In addition, the sensors will need to have as small a footprint as possible in size and power requirements. With these varied requirements in mind, only electrochemical sensors have the potential to be practical. This article focuses on nitric oxide (NO_x) and ammonia (NH₃) sensor necessary for emission control of next generation, high efficiency, lean burn engines and nitric oxide (NO) sensor for breath analysis for diagnosis of respiratory diseases. In all of these applications, there has been significant recent commercial activity. We indicate the electrochemical principles of these commercial sensors, and the development from our research group. We present potentiometric total NO_x sensors that can operate in harsh environments, and impedance-based NH₃ sensor for transportation industry. For detecting NO in human breath, we have demonstrated two strategies, the first using a resistive approach, and the second with an array of potentiometric sensors. Data from these sensors, their limitations as well as novel MEMS-based approaches for miniaturization is presented.

For a variety of application areas, including homeland defense, environmental and health monitoring and emergency response, the detection of gas-phase chemicals is of great interest. One approach to these challenging sensing tasks is to use arrays of broadly selective chemical sensors as an electronic nose. In this presentation, we describe recent research at NIST, which employs multi-element microscale chemiresistor arrays populated with varied (chemically and morphologically) sensing materials. Furthermore, we modulate the operating temperature of the microsensors on millisecond timescales to enable increased selectivity for the detection of several volatile organic compounds in air at varied concentrations less than 100 μmol/mol.

Low cost, low power and highly sensitive gas sensors operating at room temperature are very important devices for controlled hydrogen gas production and storage. One of the disadvantages of chemosensors is their high operating temperature (usually 200 – 400 °C), which excludes such type of sensors from usage in explosive environment. In this report, a new concept of gas chemosensors operating at room temperature based on TiO₂ thin films is discussed. Integration of such sensor is fully compatible with sub-100 nm semiconductor technology and could be transferred directly from labor to commercial sphere.

Titania nanotubular layers (TiO₂-NTs) are better known with their use in dye-synthesized solar cells. In the field of gas sensors, the best known application of TiO₂-NT layers is given with H₂ sensing. TiO₂–NT structures are commonly synthesized from pure titanium by anodic oxidation method. As literature indicates, gas sensing with titania can be modified by doping to obtain p- or n-type semiconductor behaviour. As undoped titania is widely used for CO and H₂- sensing, Al- and Cr-doped titania is reported to be effective for NO₂-sensing. Nanostructuring of TiO₂ yields faster and more stable response toward CO and NO₂ with almost no drift in sensor signal. Dopants are introduced by wet-chemistry method or by simultaneous anodization in an alloy. We introduced Cr³⁺ to TiO₂ NT-layers by soaking in nitrate salt and Al³⁺ by anodization of Ti6Al4V alloy. All doped TiO₂ NTs are tested for NO₂ sensing at temperatures up to 500°C in the presence of CO. The characteristics of doping are investigated by XRD, EDX-TEM methods. Cr-doping of nanotubular TiO₂ sensors displays p-type semiconductor behaviour and a considerably increased NO₂-selectivity, while Aldoping emphasizes the CO-selectivity. Effect of Cr-doping on sensing is further investigated by means of impedance spectroscopic measurements and equivalent circuit modeling in order to optimize the sensors for real-time measurements.

Active clearance control within the turbine section of gas turbine engines presents and opportunity within aerospace and industrial applications to improve operating efficiencies and the life of downstream components. Open loop clearance control is currently employed during the development of all new large core aerospace engines; however, the ability to measure the gap between the blades and the case and close down the clearance further presents as opportunity to gain even greater efficiencies. The turbine area is one of the harshest environments for long term placement of a sensor in addition to the extreme accuracy requirements required to enable closed loop clearance control. This paper gives an overview of the challenges of clearance measurements within the turbine as well as discusses the latest developments of a microwave sensor designed for this application.

III-V compound multi-junction (MJ) solar cells have great potential for space and terrestrial applications because they have high efficiency potential of more than 50% and superior radiation-resistance. Recently, more than 40% efficiency cells were reported by Fraunhofer ISE, Spectrolab, Sharp and others. Concentrator 4-junction or 5-junction solar cells have great potential for realizing super high-efficiency of over 50%. In order to realize super high-efficiency of more than 50%, it is substantially important to understand and reduce several losses of solar cells. This paper reviews loss mechanism for III-V compound solar cells and MJ solar cells. In addition, recent results under the EU-Japan Collaborative Research on Concentrator Photovoltaics are also presented. The conversion efficiency of inverted epitaxially grown InGaP/GaAs/InGaAs triple-junction solar cells has been improved to 37.9% (1-sun, AM1.5G) and 44.4% (250- 300 suns) as a result of proposing double-hetero structure wide-band-gap tunnel junctions, and inverted epitaxial growth.

Nanoscale engineering of band profile and potential profile provide effective tools for the management of photoelectron processes in quantum dot (QD) photovoltaic devices. We investigate the QD devices with various 1-μm InAs /GaAs QD media placed in a 3-μm base GaAs p-n junction. We found that n-charging of quantum dots (QDs) create potential barriers around QDs. QD growth between ultrathin AlGaAs layers leads to the formation of AlGaAs “fence” barriers, and reduces the wetting layers (WLs). The barriers around QDs and reduction of the wetting layer substantially suppress recombination processes via QDs. The n-doping of interdot space in QD media enhances electron extraction from QDs. All of our QD devices show short-circuit current, J_SC, higher than that of the reference cell, but smaller open-circuit voltage, V_OC.. In the QD devices, the short circuit currents increase by ~0.1 mA/cm² per dot layer. J_SC reaches 28.4 mA/cm² in the device with QD media that combines dot charging, fence barriers, and WL reduction.

Nanoscale integrated photonic devices and circuits offer a path to ultra-low power computation at the few-photon level. Here we propose an optical circuit that performs a ubiquitous operation: the controlled, random-access readout of a collection of stored memory phases or, equivalently, the computation of the inner product of a vector of phases with a binary selector" vector, where the arithmetic is done modulo 2pi and the result is encoded in the phase of a coherent field. This circuit, a collection of cascaded interferometers driven by a coherent input field, demonstrates the use of coherence as a computational resource, and of the use of recently-developed mathematical tools for modeling optical circuits with many coupled parts. The construction extends in a straightforward way to the computation of matrix-vector and matrix-matrix products, and, with the inclusion of an optical feedback loop, to the computation of a weighted" readout of stored memory phases. We note some applications of these circuits for error correction and for computing tasks requiring fast vector inner products, e.g. statistical classification and some machine learning algorithms.

We present progress towards the development of novel hybrid photonic-phononic oscillator technologies in both nanoscale silicon photonics and in fiber optic systems. These systems utilize traveling-wave photon-phonon couplings involving both stimulated Brillouin scattering processes (SBS). We explore numerous geometries that have enabled large forward-SBS processes in nanoscale silicon waveguides for the first time, and examine new approaches to achieving integrated Brillouin based signal processing.

3-D printing is an emerging technology that has been used primarily on small scales for rapid prototyping, but which could also herald a wider movement towards decentralized, highly customizable manufacturing. Polymers are the most common materials to be 3-D printed today, but there is great demand for a way to easily print metals. Existing techniques for 3-D printing metals tend to be expensive and energy-intensive, and usually require high temperatures or pressures, making them incompatible with polymers, organics, soft materials, and biological materials. Here, we describe room temperature liquid metals as complements to polymers for 3-D printing applications. These metals enable the fabrication of soft, flexible, and stretchable devices. We survey potential room temperature liquid metal candidates and describe the benefits of gallium and its alloys for these purposes. We demonstrate the direct printing of a liquid gallium alloy in both 2-D and 3-D and highlight the structures and shapes that can be fabricated using these processes.

Soft, bioelectronics interfaces are broadly defined as microfabricated devices with mechanical properties suited to comply with biological tissues. There are many challenges associated with the development of such technology platforms. Simultaneously one must achieve reliable electronic performance, thermal and environmental stability, mechanical compliance, and biocompatibility. Materials and system architecture must be designed such that mechanical integrity and electrical functionality is preserved during fabrication, implementation and use of the interface. Depositing and patterning conventional device materials, ranging from inorganic to organic thin films as well as nanomaterials, directly onto soft elastomeric substrates enable electronic devices with enhanced mechanical flexibility. Success in fabrication also relies on a careful design of the mechanical architecture of the soft interface to minimize mechanical stresses in the most fragile materials.

Thin, lightweight and flexible electronics are being regarded as an important evolutionary step in the development of novel technological products. Interestingly, this trend has emerged in a wide range of industries; from microelectronics to photovoltaics and even solid state lighting. Historically, most attempts to enable flexibility have focused on the introduction of new material systems that, so far, severely compromise the performance compared to state-of-the-art products. The few approaches that do attempt to render contemporary high-performance materials flexible rely on layer transfer techniques that are complicated, expensive and material-specific. In this paper, we review a method of removing surface layers from brittle substrates called Controlled Spalling Technology that allows one to simple peel material or device layers from their host substrate after they have been fabricated. This allows one to fabricate high-performance electronic products in a manner of their choosing, and make them flexible afterwards. This technique is simple, inexpensive and largely independent of substrate material or size. We demonstrate the power and generality of Controlled Spalling by application to a number of disparate applications including high-performance integrated circuits, high-efficiency photovoltaics and GaN-based solid state lighting.

In recent years, personalized electronics for medical applications, particularly, have attracted much attention with the rise of smartphones because the coupling of such devices and smartphones enables the continuous health-monitoring in patients’ daily life. Especially, it is expected that the high performance biomedical electronics integrated with the human body can open new opportunities in the ubiquitous healthcare. However, the mechanical and geometrical constraints inherent in all standard forms of high performance rigid wafer-based electronics raise unique integration challenges with biotic entities. Here, we describe materials and design constructs for high performance skin-mountable bio-integrated electronic devices, which incorporate arrays of single crystalline inorganic nanomembranes. The resulting electronic devices include flexible and stretchable electrophysiology electrodes and sensors coupled with active electronic components. These advances in bio-integrated systems create new directions in the personalized health monitoring and/or human-machine interfaces.

We report the demonstration of bendable inductors, capacitors and switches fabricated on a polyethylene terephthalate (PET) substrate that can operate at high microwave frequencies. By employing bendable dielectric and single crystalline semiconductor materials, spiral inductors and metal-insulator-metal (MIM) capacitors with high quality factors and high resonance frequencies and single-pole, single-throw (SPST) switches were archived. The effects of mechanical bending on the performance of inductors, capacitors and switches were also measured and analyzed. We further investigated the highest possible resonance frequencies and quality factors of inductors and capacitors and, high frequency responses and insertion loss. These demonstrations will lead to flexible radio-frequency and microwave systems in the future.

Flexible electronics and photonics are providing revolutionary solutions for communication, energy, and health care. While some of the organic electronic and photonic materials are intrinsically deformable and low cost to manufacture, their performance and chemical stabilities are yet to match conventional inorganic semiconductors. Strategies for high performance flexible electronics and photonics must overcome challenges associated with the intrinsic stiffness and brittleness of inorganic materials. This paper discusses recent modeling and experimental advancement in the bendability and stretchability of inorganic electronics and photonics. Examples include the discovery of multiple neutral axes in multilayer structures and the comparison between freestanding and polymer-bonded serpentine ribbons.

With the emergence of cloud computation, we are facing the rising waves of big data. It is our time to leverage such opportunity by increasing data usage both by man and machine. We need ultra-mobile computation with high data processing speed, ultra-large memory, energy efficiency and multi-functionality. Additionally, we have to deploy energy-efficient multi-functional 3D ICs for robust cyber-physical system establishment. To achieve such lofty goals we have to mimic human brain, which is inarguably the world’s most powerful and energy efficient computer. Brain’s cortex has folded architecture to increase surface area in an ultra-compact space to contain its neuron and synapses. Therefore, it is imperative to overcome two integration challenges: (i) finding out a low-cost 3D IC fabrication process and (ii) foldable substrates creation with ultra-large-scale-integration of high performance energy efficient electronics. Hence, we show a low-cost generic batch process based on trench-protect-peel-recycle to fabricate rigid and flexible 3D ICs as well as high performance flexible electronics. As of today we have made every single component to make a fully flexible computer including non-planar state-of-the-art FinFETs. Additionally we have demonstrated various solid-state memory, movable MEMS devices, energy harvesting and storage components. To show the versatility of our process, we have extended our process towards other inorganic semiconductor substrates such as silicon germanium and III-V materials. Finally, we report first ever fully flexible programmable silicon based microprocessor towards foldable brain computation and wirelessly programmable stretchable and flexible thermal patch for pain management for smart bionics.

In nature, arthropods have a remarkably sophisticated class of imaging systems, with a hemispherical geometry, a wideangle field of view, low aberrations, high acuity to motion and an infinite depth of field. There are great interests in building systems with similar geometries and properties due to numerous potential applications. However, the established semiconductor sensor technologies and optics are essentially planar, which experience great challenges in building such systems with hemispherical, compound apposition layouts. With the recent advancement of stretchable optoelectronics, we have successfully developed strategies to build a fully functional artificial apposition compound eye camera by combining optics, materials and mechanics principles. The strategies start with fabricating stretchable arrays of thin silicon photodetectors and elastomeric optical elements in planar geometries, which are then precisely aligned and integrated, and elastically transformed to hemispherical shapes. This imaging device demonstrates nearly full hemispherical shape (about 160 degrees), with densely packed artificial ommatidia. The number of ommatidia (180) is comparable to those of the eyes of fire ants and bark beetles. We have illustrated key features of operation of compound eyes through experimental imaging results and quantitative ray-tracing-based simulations. The general strategies shown in this development could be applicable to other compound eye devices, such as those inspired by moths and lacewings (refracting superposition eyes), lobster and shrimp (reflecting superposition eyes), and houseflies (neural superposition eyes).

Electronically-enabled wearable systems that monitor physiological activity and electrophysiological activity hold the key to truly personalized medical care outside of the hospital setting. However, fundamental technical challenges exist in achieving medical systems that are comfortable, unobtrusive and fully integrated without external connections to bench top instruments. In particular, there is a fundamental mismatch in mechanical coupling between existing classes of rigid electronics and soft biological substrates, like the skin. Here we describe new mechanical and electrical design strategies for wearable devices with mechanical properties that approach that of biological tissue. These systems exploit stretchable networks of conformal sensors (i.e. electrodes, temperature sensors, and accelerometers) and associated circuitry (i.e. microcontroller, memory, voltage regulators, rechargeable battery, wireless communication modules) embedded in ultrathin, elastomeric substrates. Quantitative analyses of sensor performance and mechanics under tensile and torsional stresses illustrate the ability to mechanically couple with soft tissues in a way that is mechanically invisible to the user. Representative examples of these soft biointegrated systems can be applied for continuous sensing of muscle and movement activity in the home and ambulatory settings.

Two-dimensional atomic sheets have emerged as near ideal nanomaterials to overcome the long running challenge of achieving Si CMOS like performance on soft substrates at scales that can be suitable for large integration. For instance, the high mobility and velocity accessible in monolayer graphene affords GHz analog transistor devices while the large bandgap of graphene’s semiconducting analogues (MoS2 and similar dichalcogenides) naturally lead to near ideal digital transistors with high on/off current ratio and low subthreshold slope while sustaining mobilities much larger than organic semiconductors or amorphous bulk semiconductors. Together, these physically similar atomic layers with vastly different electronic properties can serve as the electronic platform for low-power digital, high-speed mixed-signal, and high-frequency analog transistor building blocks for flexible nanoelectronic systems. Here we report GHz graphene transistors operating in the microwave frequency range, and address mobility and contact resistance extraction in semiconducting atomic sheets. Further progress on heterogeneous integration of graphene and 2D semiconducting crystals can enable future flexible nanosystems.

We present two potential flow based computational tools for the design and analysis of efficient, low Reynolds number flapping wings. Our approach starts with a series of wake-only momentum and energetics analyses. We have used and extended the classical wake-only approach to efficiently perform a large number of computations over the flapping parameter space. The method considers the balance of flight forces in the coupled prediction of wing flapping kinematics and flight energetics. Following the wake-only energetics analysis, a quasi-inverse doublet lattice method (qi-DLM) is applied to determine flapping wing shape including localized wing morphing and deformation. This local wing morphing prescribed so that the wing may achieve the desired, minimum power wake vorticity distribution defined by the wake-only analysis. In this paper we illustrate these methods and perform a preliminary study to assess the impact of wing taper, wing camber and wing twist variations on efficient flapping flight.

Commercially available speed controllers, motors, and propellers typically comprise the powertrains of many micro aerial robotic systems, such as quadrotor vehicles. As on board state sensing and processing improves, actuation bandwidth is becoming a significant bottleneck that limits the performance of the entire closed loop system. The performance of the commercial products can be greatly enhanced through the implementation of classical control methods directly at the powertrain level. In this paper, reduced order open loop models for three representative commercially available powertrains were estimated and were compared with closed loop equivalents. Further performance improvement is realized by the addition of a static inverse to mitigate the steady state structured uncertainty of the system.

The development of autonomous Micro Aerial Vehicles (MAVs) is significantly constrained by their size, weight and power consumption. In this paper, we explore the energetics of quadrotor platforms and study the scaling of mass, inertia, lift and drag with their characteristic length. The effects of length scale on masses and inertias associated with various components are also investigated. Additionally, a study of Lithium Polymer battery performance is presented in terms of specific power and specific energy. Finally, we describe the power and energy consumption for different quadrotors and explore the dependence on size and mass for static hover tests as well as representative maneuvers.

Within the past few years micro aerial vehicles (MAVs) have received much more attention and are starting to proliferate into military as well as civilian roles. However, one of the major drawbacks for this technology currently, has been their poor endurance, usually below 10 minutes. This is a direct result of the inefficiencies inherent in their design. Often times, designers do not consider the various components in the vehicle design and match their performance to the desired mission for the vehicle. These vehicles lack a prescribed set of design guidelines or empirically derived design equations which often limits their design to selection of commercial off-the-shelf components without proper consideration of their affect on vehicle performance. In the current study, the design space for different vehicle configurations has been examined including insect flapping, avian flapping, rotary wing, and fixed wing, and their performance bounds are established. The propulsion system typical of a rotary wing vehicle is analyzed to establish current baselines for efficiency of vehicles at this scale. The power draw from communications is analyzed to determine its impact on vehicle performance. Finally, a representative fixed wing MAV is examined and the effects of adaptive structures as a means for increasing vehicle endurance and range are examined. This paper seeks to establish the performance bounds for micro air vehicles and establish a path forward for future designs so that efficiency may be maximized.

The past decade has seen an increased interest towards research involving Autonomous Micro Aerial Vehicles (MAVs). The predominant reason for this is their agility and ability to perform tasks too difficult or dangerous for their human counterparts and to navigate into places where ground robots cannot reach. Among MAVs, rotary wing aircraft such as quadrotors have the ability to operate in confined spaces, hover at a given point in space and perch1 or land on a flat surface. This makes the quadrotor a very attractive aerial platform giving rise to a myriad of research opportunities. The potential of these aerial platforms is severely limited by the constraints on the flight time due to limited battery capacity. This in turn arises from limits on the payload of these rotorcraft. By automating the battery recharging process, creating autonomous MAVs that can recharge their on-board batteries without any human intervention and by employing a team of such agents, the overall mission time can be greatly increased. This paper describes the development, testing, and implementation of a system of autonomous charging stations for a team of Micro Aerial Vehicles. This system was used to perform fully autonomous long-term multi-agent aerial surveillance experiments with persistent station keeping. The scalability of the algorithm used in the experiments described in this paper was also tested by simulating a persistence surveillance scenario for 10 MAVs and charging stations. Finally, this system was successfully implemented to perform a 9½ hour multi-agent persistent flight test. Preliminary implementation of this charging system in experiments involving construction of cubic structures with quadrotors showed a three-fold increase in effective mission time.

This paper summarizes work towards creating mm-scale power converters using high-frequency CMOS as well as MEMS and micro-machined passives. Reducing the converter size is largely motivated by creating power supplies for micro-robotic platforms (with millimeter and milligram scales) without negatively impacting robotic system functionality. MEMS power passives are first presented where thin-film piezoelectric transformers and resonators are shown as an electromechanical approach to achieve ultra-miniature passives at the chip scale. Piezoelectric transformers fabricated with thin-film lead zirconate titanate (PZT) on silicon are measured and show ~60% efficiencies with 240 and 75 Ω loads. These transformers have resonant frequencies ranging between 14 and 20 MHz. Work towards creating transmission lines fabricated with air-core inductors and ferroelectric capacitors is also presented. Finally, a fullyintegrated bi-directional converter in CMOS is shown driving mm-scale robotic wings made with PZT. The converter’s maximum efficiency is 77% at ~800μW load with 9V output and demonstrates <3x voltage boost in 0.13-μm triple-well CMOS.

Contemporary electronic systems often contain power circuits to support the unique power conversion or conditioning needs of each of the various subsystems. Each of these power circuits is generally implemented with discrete passive and active electronic components soldered next to the load devices on the printed circuit board. As greater levels of functionality are demanded within diminishing size and weight allowances, power management solutions will increasingly demand highly miniaturized power converters that are more tightly integrated into single-package solutions or even directly integrated onto the points of source and load. Experimental converters have demonstrated great potential in switching at very high frequencies (100+ MHz) to reduce the size of the requisite passive storage elements (inductors, transformers, and capacitors) to values that may be suitable for in-package or on-chip integration. However, integrating the passives into the same package as the active switching and control circuitry remains a significant fabrication challenge due to material incompatibility and inadequate performance of the passives. This paper discusses progress towards a fully integrated power converter module with a focus on microfabrication processes for both passive component development and wafer-level packaging. The passive components have been optimized for high performance at hundreds of MHz through the use of thick copper traces, intricate three-dimensional winding patterns. The capability of detaching the passives from the fabrication wafer produces a passives substrate that can serve directly as a routing platform for full integration of all components into a single-package solution.

Micro air vehicles developed under the Army’s Micro Autonomous Systems and Technology program generally need a specific energy of 300 – 550 watt-hrs/kg and 300 -550 watts/kg to operate for about 1 hour. At present, no commercial cell can fulfill this need. The best available commercial technology is the Lithium-ion battery or its derivative, the Li- Polymer cell. This chemistry generally provides around 15 minutes flying time. One alternative to the State-of-the Art is the Al/air cell, a primary battery that is actually half fuel cell. It has a high energy battery like aluminum anode, and fuel cell like air electrode that can extract oxygen out of the ambient air rather than carrying it. Both of these features tend to contribute to a high specific energy (watt-hrs/kg). High specific power (watts/kg) is supported by high concentration KOH electrolyte, a high quality commercial air electrode, and forced air convection from the vehicles rotors. The performance of this cell with these attributes is projected to be 500 watt-hrs/kg and 500 watts/kg based on simple model. It is expected to support a flying time of approximately 1 hour in any vehicle in which the usual limit is 15 minutes.

The quest for developing clean, quiet, and portable high energy density, and ultra-compact power sources continues. Although batteries offer a well known solution, limits on the chemistry developed to date constrain the energy density to 0.2 kWh/kg, whereas many hydrocarbon fuels have energy densities closer to 13 kWh/kg. The fundamental challenge remains: how efficiently and robustly can these widely available chemical fuels be converted into electricity in a millimeter to centimeter scale systems? Here we explore two promising technologies for high energy density power generators: thermophotovoltaics (TPV) and thermoelectrics (TE). These heat to electricity conversion processes are appealing because they are fully static leading to quiet and robust operation, allow for multifuel operation due to the ease of generating heat, and offer high power densities. We will present some previous work done in the TPV and TE fields. In addition we will outline the common technological barriers facing both approaches, as well as outline the main differences. Performance for state of the art research generators will be compared as well as projections for future practically achievable systems. A viable TPV or TE power source for a ten watt for one week mission can be built from a <10% efficient device which is achievable with current state of the art technology such as photonic crystals or advanced TE materials.

This paper outlines alternative uses of block copolymer (BCP) patterning compared to their well-researched exploitation in defining silicon circuitry and interconnects. The challenge in these alternative applications is usually to define ‘active’ patterns of materials other than silicon and instead of using the self-assembled block copolymer pattern as a means to form an on-chip etch mask, to use it as a template for deposition of functional components. In this paper we briefly discuss progress in the field of block copolymer patterning and some potential applications. The paper will then outline two examples in the area of sensing and antimicrobial surfaces. Here, polystyrene-b-polyethylene oxide (PS-b-PEO) is used as a suitable template as it forms well-ordered arrangements on several substrate types. The PEO block can then be used as a host block towards precursor inclusion from solution because of its’ selective chemistry. Onward processing then creates a pattern of included materials that mimics the original BCP arrangement. To demonstrate the potential of these methods we illustrate examples as sensors and antimicrobial surfaces which both take advantage of the small feature size, high surface area and coverage that can be attained by these techniques.

Block copolymer thin films provide a robust method for generating regular, uniform patterns with sub-100 nanometer length scales over arbitrarily large areas. A significant advantage of such block copolymer-based patterning is its ease of integration with all other aspects of traditional thin-film processing, including plasma-based etching and metallization. Such process compatibility ensures a host of application opportunities in designing material properties through control of their nanostructure. Here, we describe our use of block copolymer self assembly for design and vapor phase synthesis of quasi one-dimensional nanostructured materials made of metals, semiconductors, and insulators. The precise control of surface texture afforded by block copolymer-based patterning can influence macroscopic materials properties such as optical reflectance and hydrophobicity.

The self-assembly of soft matter, such as block copolymers or colloids, allows fine tuning of structure formation on the 10 - 500nm length scale and therefore enables the design of materials with tunable optical response. We present strategies on how to exploit these formation principles to assemble inorganic nanoarchitectures with distinct optical properties and point out promising applications in photovoltaics, colorimetric sensing and self-cleaning antireflective coatings.

Whole-body PET is currently limited by the degradation due to patient motion. Respiratory motion degrades imaging studies of the abdomen. Similarly, both respiratory and cardiac motions significantly hamper the assessment of myocardial ischemia and/or metabolism in perfusion and viability cardiac PET studies. Based on simultaneous PET-MR, we have developed robust and accurate MRI methods allowing the tracking and measurement of both respiratory and cardiac motions during abdominal or cardiac studies. Our list-mode iterative PET reconstruction framework incorporates the measured motion fields into PET emission system matrix as well as the time-dependent PET attenuation map and the position dependent point spread function. Our method significantly enhances the PET image quality as compared to conventional methods.

Technological advances in imaging systems and the development of target specific imaging tracers has been rapidly growing over the past two decades. Recent progress in “all-in-one” imaging systems that allow for automated image coregistration has significantly added to the growth of this field. These developments include ultra high resolution PET and SPECT scanners that can be integrated with CT or MR resulting in PET/CT, SPECT/CT, SPECT/PET and PET/MRI scanners for simultaneous high resolution high sensitivity anatomical and functional imaging. These technological developments have also resulted in drastic enhancements in image quality and acquisition time while eliminating cross compatibility issues between modalities. Furthermore, the most cutting edge technology, though mostly preclinical, also allows for simultaneous multimodality multi-isotope image acquisition and image reconstruction based on radioisotope decay characteristics. These scientific advances, in conjunction with the explosion in the development of highly specific multimodality molecular imaging agents, may aid in realizing simultaneous imaging of multiple biological processes and pave the way towards more efficient diagnosis and improved patient care.

NASA's Earth Science Technology Office (ESTO) performs strategic investments in instrument subsystems, information systems, and most recently the use of CubeSat platforms to advance the technology readiness level (TRL) of relevant Earth Science Decadal Survey technologies to reduce and retire risk before infusion into flight missions. In this talk we describe the ESTO philosophy to strategic investment focusing on radiometer technology development and testing including new work involving spaceborne flight validation of radiometer technologies using CubeSats.

Two thematic drivers are motivating the science community towards constellations of small satellites, the revelation that many next generation system science questions are uniquely addressed with sufficient numbers of simultaneous space based measurements, and the realization that space is historically expensive, and in an environment of constrained costs, we must innovate to ―do more with less‖. We present analysis that answers many of the key questions surrounding constellations of scientific satellites, including research that resulted from the GEOScan community based effort originally intended as hosted payloads on Iridium NEXT. We present analysis that answers the question how many satellites does global system science require? Perhaps serendipitously, the analyses show that many of the key science questions independently converge towards similar results, i.e. that approximately 60+ satellites are needed for transformative, as opposed to incremental capability in system science. The current challenge is how to effectively transition products from design to mass production for space based instruments and vehicles. Ideally, the lesson learned from past designs and builds of various space products should pave the way toward a better manufacturing plan that utilizes just a fraction of the prototype‘s cost. Using the commercial products industry implementations of mass customization as an example, we will discuss about the benefits of standardization in design requirements for space instruments and vehicles. For example, the instruments (payloads) are designed to have standardized elements, components, or modules that interchangeably work together within a linkage system. We conclude with a discussion on implementation plans and the new paradigms for community and international cooperation enabled by small satellite constellations.

Detecting energetic particles is a useful approach in studying space plasmas. Of specific interest are energetic neutral atoms (ENA) because their trajectories are unaffected by electric or magnetic fields. Imaging the ENA flux allows for the mapping of remote plasmas. In order to detect such particles, solid-state detectors are advantageous due to their lightweight and low power. However in the sensing environment the photon flux is usually several orders of magnitude higher than the ENA flux. Thus, in order to detect the energetic particles the photon flux must be blocked. Therefore, thin metal or carbon film filters that allow the transmission of ENAs while attenuating the photon signal are used. Here we report tests of low-density mats of carbon nanotubes (CNTs) as a filter medium. For a given mass per unit area (the parameter which sets the particle transmission energy threshold), CNTs are expected to absorb photons significantly better than thin films. The CNTs were grown by a water assisted chemical vapor deposition technique and pulled from their substrate to generate a CNT sheet covering an aperture. In order to test the performance of the CNT sheet as a filter, the transmissions of light and alpha particles were measured. We were able to achieve filter performance that resulted in alpha particle energy loss of only 5 keV with an optical density of 0.5.

The detection of concealed weapons in crowd situations is a critical need and solutions are being sought after by security agencies at the federal, state and municipal levels. Millimeter waves have been evaluated for these kinds of applications, but the currently available technologies are typically too large and bulky to allow for widespread deployment. Alternatively soft X-rays have been considered but safety issues hinder their acceptance. Terahertz technology is ideally suited for such an application as it has the ability to see through clothing, and offers higher resolution than in the millimeter band, also being more compact. THz photons have lower energy than infrared and do not show the ionizing properties of X-ray radiation. The longer Terahertz waves penetrate deeper into various materials then their visible and infrared counterparts. Though the wavelength is longer it has been shown that high resolution in a small form factor can be obtained in the THz wavebands thanks to the use of small pixel pitch detectors. In this paper, a case study for the use of a compact THz camera for active see-through imaging at stand-off distances is presented. More specifically, the cases of seeing through packages and clothing are analyzed in the perspective of concealed weapons detection. The paper starts with a review of the characteristics of a high resolution THz camera exhibiting small pixel size and large field-of-view. Some laboratory results of concealed object imaging along with details of a concept for live surveillance using a compact see-through imaging system are reviewed.

Bleaching by ultra-short pulses is discussed as an opportunity for semiconductor optical augmentation. The ability of ultra-short laser pulse to excite and remove electrons in-bulk from valence band may be used to prevent generation of thermal electrons for extended period of time. That time is correlated with recombination time. Diminishing the number of electrons that are available for thermal excitation leads to thermal noise reduction in the same way as semiconductor cooling. Technology based on the effect may be used as effective alternative to thermal cooling, and may allow some semiconductors effectively be exploited at ambient temperatures. Specifically, high sensitive and fast detectors as well as semiconductor lasers covering long and very long-wavelengths may actually work without extra cooling., needed to reduce thermal noise. In this paper, we will consider the effects caused by relatively low pulse energy ultra-short pulse lasers.

Chemical sensors based on micro/nanoelectromechanical systems (M/NEMS) offer many advantages. However, obtaining chemical selectivity in M/NEMS sensors using chemoselective interfaces has been a longstanding challenge. Despite their many advantages, M/NEMS devices relying on chemoselective interfaces do not have sufficient selectivity. Therefore, highly sensitive and selective detection and quantification of chemical molecules using real-time, miniature sensor platforms still remains as a crucial challenge. Incorporating photothermal/photoacoustic spectroscopic techniques with M/NEMS using quantum cascade lasers can provide the chemical selectivity without sacrificing the sensitivity of the miniaturized sensing system. Point sensing is defined as sensing that requires collection and delivery of the target molecules to the sensor for detection and analysis. For example, photothermal cantilever deflection spectroscopy, which combines the high thermomechanical sensitivity of a bimetallic microcantilever with high selectivity of the mid infrared (IR) spectroscopy, is capable of obtaining molecular signatures of extremely small quantities of adsorbed explosive molecules (tens of picogram). On the other hand, standoff sensing is defined as sensing where the sensor and the operator are at distance from the target samples. Therefore, the standoff sensing is a non-contact method of obtaining molecular signatures without sample collection and processing. The distance of detection depends on the power of IR source, the sensitivity of a detector, and the efficiency of the collecting optics. By employing broadly tunable, high power quantum cascade lasers and a boxcar averager, molecular recognition of trace explosive compounds (1 μg/cm² of RDX) on a stainless steel surface has been achieved at a distance of five meters.

Hyperspectral instruments with physical sizes comparable to that of a bare sensing array are now possible. Compact Fabry-Perot (FP) etalon arrays allow for different spectral sensitivities to be assigned to the different pixels of a sensing array. Such arrays for hyperspectral imaging are commercially available but underutilized due to cost and performance tradeoffs. FP arrays were first made possible by binary or logarithmic fabrication, which reduces the number of lithography steps to log₂(k) where k is the number of distinct levels of material required for the integrated optical element. However, significant yield loss results from the several lithography steps required in this process. We introduce a new binary etching technique that allows for the creation of an arbitrary number of distinct levels with a single greyscale lithography technique. Our technique has been used for the fabrication of distinct levels of 1 nm rms flatness with a controlled 10 nm resolution. This technique has been used to fabricate a staircase structure with greater than 100 distinct steps directly on a COTS optical imager. Details of the fabrication technique and characteristics of the optical element will be presented.

We have invented a novel photodetector by mating a surface plasmon resonance coupler with a graphene field effect transistor. The device enables wavelength selectivity for spectral sensing applications. Surface plasmon polaritons (SPPs) are generated in a 50 nm thick Ag film on the surface of a prism in the Kretschmann configuration positioned 500 nm from a graphene FET. Incident photons of a given wavelength excite SPPs at a specific incidence angle. These SPP fields excite a transient current whose amplitude follows the angular resonance spectrum of the SPP absorption feature. Though demonstrated first at visible wavelengths, the approach can be extended far into the infrared. We also demonstrate that the resonant current is strongly modulated by gate bias applied to the FET, providing a clear path towards large-scale spectral imagers with locally addressable pixels.

With the end goal of medical applications such as non-invasive surgery and targeted drug delivery, an acoustically driven resonant structure is proposed for microrobotic propulsion. At the proposed scale, the low Reynolds number environment requires non-reciprocal motion from the robotic structure for propulsion; thus, a “flapper” with multiple, flexible joints, has been designed to produce excitation modes that involve the necessary flagella-like bending for non-reciprocal motion. The key design aspect of the flapper structure involves a very thin joint that allows bending in one (vertical) direction, but not the opposing direction. This allows for the second mass and joint to bend in a manner similar to a dolphin’s “kick” at the bottom of their stroke, resulting in forward thrust. A 130 mm x 50 mm x 0.2 mm prototype of a swimming robot that utilizes the flapper was fabricated out of acrylic using a laser cutter. The robot was tested in water and in a water-glycerine solution designed to mimic microscale fluid conditions. The robot exhibited forward propulsion when excited by an underwater speaker at its resonance mode, with velocities up to 2.5 mm/s. The robot also displayed frequency selectivity, leading to the possibility of exploring a steering mechanism with alternatively tuned flappers. Additional tests were conducted with a robot at a reduced size scale.

Multilevel controllable nanoimprint driven molecular orientation has been obtained in thin films of block copolymer polystyrene-b-polyethylene oxide( PS-b-PEO) by means of solvent vapours assisted nanoimprint lithography (SAIL). The NIL setup using solvent vapours was capable of imprinting nanoscale features over a large area and simultaneously annealing PS-b-PEO thin films. A line pattern stamp was replicated in the BCP film in over a large area with a high resolution registry, and was also observed that the PS-b-PEO film exhibited microphase segregation in the residual layer exhibits a nanodot array from showing hexagonally packed PEO dots in the PS matrix, with a diameter of 20 nm with 40 nm pitch. The order of the hexagonally arranged nanodot lattice seen in the nanodots array was quantified from SEM images using by the opposite partner method from SEM images analysis and compared with to conventionally solvent annealed BCP films, demonstrating an improvement of the ordering of up to 50%. Grazing-incidence small-angle X-ray scattering (GISAXS) study demonstrates the excellent fidelity of the pattern transfer and confirms the periodicity of the BCP in the mesas. In addition, applying the SAIL methodology to BCP thin films in nanopatterned silsequioxane substrates, it was possible to obtain multilevel structures decorated with the BCP microphase segregation. The SAIL technique is a versatile and robust platform to obtain complex high density periodic nanostructures, particularly for second generation block copolymers directed self-assembly.

In this article we demonstrate a method based on Transfer Matrix (TMM) that can be used to analyze optical properties of multilayered thin films and planar metamaterials for terahertz (THz) detection. Producing and testing such films require host substrates that can be up to 4 orders of magnitude thicker than the THz-sensitive films. Therefore, the ability to efficiently model, simulate and accurately predict the optical properties of multilayered structures, with significant differences in thickness, is crucial to designing sensors with maximized absorption. This method, which provides an analytical tool, less computationally intensive then finite element modeling, can be used for films composed of any number of layers with arbitrary thicknesses, aspect ratios and arbitrary angles of incidence. Homogeneous or patterned (metamaterials) films can be modeled enabling accurate analysis of positive and negative index materials indistinctly. Reflection, transmission and absorption of metallic/dielectric nanolaminates, metallic thin films and planar metamaterial films are analyzed and compared with experimental measurements and FE simulations. Results show good agreement for a wide range of structures, materials and frequencies and indicate that the method has a great potential for design and optimization of sophisticated multilayered structures for THz detection and beyond.

We have designed and tested a prototype TRL4 radio-frequency (RF) sensing platform containing a transceiver that interrogates a passive carbon nanotube (CNT)–based sensor platform. The transceiver can be interfaced to a server technology such as a Bluetooth® or Wi-Fi device for further connectivity. The novelty of a very-low-frequency (VLF) implementation in the transceiver design will ultimately enable deep penetration into the ground or metal structures to communicate with buried sensing platforms. The sensor platform generally consists of printed electronic devices made of CNTs on flexible poly(ethylene terephthalate) (PET) and Kapton® substrates. This novel remote sensing system can be integrated with both passive and active sensing platforms. It offers unique characteristics suitable for a variety of sensing applications. The proposed sensing platforms can take on different form factors and the RF output of the sensing platforms could be modulated by humidity, temperature, pressure, strain, or vibration signals. Resonant structures were designed and constructed to operate in the very-high-frequency (VHF) and VLF ranges. In this presentation, we will report results of our continued effort to develop a commercially viable transceiver capable of interrogating the conformally mounted sensing platforms made from CNTs or silver-based nanomaterials on polyimide substrates over a broad range of frequencies. The overall performance of the sensing system with different sensing elements and at different frequency ranges will be discussed.

We propose and extensively analyze a novel Graphene-FET (GFET) with two capacitively coupled field-controlling electrodes (FCE) at the ungated access regions between gate and source/drain. The FCEs are proposed to be positioned both on top and bottom of the device. The FCEs could be independently biased to modulate sheet carrier concentration and thereby the resistance in the ungated regions. The reduction of source/drain access resistance results in increased cut off frequency compared to those of conventional GFETs with the same geometry. The DC and improved RF characteristics of the proposed device have been studied using both analytical and numerical techniques and compared with the baseline designs.

We present an experimental demonstration of a novel, integrated readout approach for measuring the suspended height of micro-electro-mechanical systems (MEMS) structures. The approach is based on creating a resonant optical cavity between the suspended MEMS structure and the substrate that the MEMS structure is anchored to. The resulting interferometric effect causes modulation of an optical laser signal which is strongly dependent on the position of the MEMS device.

NEMS are rapidly being developed for a variety of sensing applications as well as for exploring interesting regimes in fundamental physics. In most of these endeavors, operation of a NEMS device involves actuating the device harmonically around its fundamental resonance and detecting subsequent motion while the device interacts with its environment. Even though a single NEMS resonator is exceptionally sensitive, a typical application, such as sensing or signal processing, requires the detection of signals from many resonators distributed over the surface of a chip. Therefore, one of the key technological challenges in the field of NEMS is development of multiplexed measurement techniques to detect the motion of a large number of NEMS resonators simultaneously. In this work, we address the important and difficult problem of interfacing with a large number of NEMS devices and facilitating the use of such arrays in, for example, sensing and signal processing applications. We report a versatile, all-optical technique to excite and read-out a distributed NEMS array. The NEMS array is driven by a distributed, intensity-modulated, optical pump through the photothermal effect. The ensuing vibrational response of the array is multiplexed onto a single, probe beam as a high-frequency phase modulation. The phase modulation is optically down converted to a low-frequency, intensity modulation using an adaptive full -field interferometer, and subsequently is detected using a charge-coupled device (CCD) array. Rapid and single-step mechanical characterization of approximately 60 nominally identical, high-frequency resonators is demonstrated. The technique may enable sensitivity improvements over single NEMS resonators by averaging signals coming from a multitude of devices in the array. In addition, the diffraction-limited spatial resolution may allow for position-dependent read-out of NEMS sensor chips for sensing multiple analytes or spatially inhomogeneous forces.

Due to the multiple scattering of light in turbid media such as biological tissues, the image of target becomes highly deteriorated and even disappears entirely. Only speckle patterns, which result from multiple scattering and interference in turbid media and contain disordered objects-information, can be acquired. Two typical methods to recover the image of target behind a turbid medium are described and simulated in this paper. The first approach is based on image correlation and wavefront shaping technique, in which the Pearson correlation coefficient is applied as a cost function for the optimization and genetic algorithm (GA) is employed to control a spatial light modulator to generate the optimal wavefront to maximize the cost function. For the second approach, the target images can be reconstructed from the speckle patterns with total variation minimization by augmented Lagrangian and alternating direction algorithms (TVAL3). Circular Gaussian distribution model and Fresnel diffraction theory are exploited in our simulations to describe turbid media and light propagation between optical devices, respectively. The anti-noise capabilities of the two methods are analyzed to demonstrate their stabilities applied in low signal-to-noise environment. This work will be beneficial to the fields of microscopic imaging and biomedical imaging in micro/nano scale.

Tornado Spectral Systems has developed a new chip-based spectrometer called OCTANE, the Optical Coherence Tomography Advanced Nanophotonic Engine, built using a planar lightwave circuit with integrated waveguides fabricated on a silicon wafer. While designed for spectral domain optical coherence tomography (SD-OCT) systems, the same miniaturized technology can be applied to many other spectroscopic applications. The field of integrated optics enables the design of complex optical systems which are monolithically integrated on silicon chips. The form factors of these systems can be significantly smaller, more robust and less expensive than their equivalent free-space counterparts. Fabrication techniques and material systems developed for microelectronics have previously been adapted for integrated optics in the telecom industry, where millions of chip-based components are used to power the optical backbone of the internet. We have further adapted the photonic technology platform for spectroscopy applications, allowing unheard-of economies of scale for these types of optical devices. Instead of changing lenses and aligning systems, these devices are accurately designed programmatically and are easily customized for specific applications. Spectrometers using integrated optics have large advantages in systems where size, robustness and cost matter: field-deployable devices, UAVs, UUVs, satellites, handheld scanning and more. We will discuss the performance characteristics of our chip-based spectrometers and the type of spectral sensing applications enabled by this technology.

It has been argued that the isolation of monolayer graphene is among the most important discoveries in the last half century. Graphene has led to new thinking about how to address persistent challenges faced by traditional material systems. A long-standing problem faced by the particle accelerator community is that of limited lifetime of electron sources. These sources launch the electron beam which is bunched and accelerated to high energies for many different applications, ranging from next generation user facilities for discovery science to directed energy systems for defense and environmental needs. Addressing limited lifetime of electron sources is a complicated problem, but we have made progress toward developing a methodology to use multiple graphene layers as a monolayer ruggedizing shield which does not appreciably disrupt photoemission but does provide a barrier isolation which could increase cathode lifetime. We present key results to date which enable graphene to function as a monolayer shield for sensitive photocathode films.