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Infrared (IR) spectroscopy is widely recognized as a gold standard technique for chemical and biological analysis. Traditional IR spectroscopy relies on fragile bench-top instruments located in dedicated laboratory settings, and is thus not suitable for emerging field-deployed applications such as in-line industrial process control, environmental monitoring, and point-of-care diagnosis. Recent strides in photonic integration technologies provide a promising route towards enabling miniaturized, rugged platforms for IR spectroscopic analysis. It is therefore attempting to simply replace the bulky discrete optical elements used in conventional IR spectroscopy with their on-chip counterparts. This size down-scaling approach, however, cripples the system performance as both the sensitivity of spectroscopic sensors and spectral resolution of spectrometers scale with optical path length. In light of this challenge, we will discuss two novel photonic device designs uniquely capable of reaping performance benefits from microphotonic scaling. We leverage strong optical and thermal confinement in judiciously designed micro-cavities to circumvent the thermal diffusion and optical diffraction limits in conventional photothermal sensors and achieve a record 104 photothermal sensitivity enhancement. In the second example, an on-chip spectrometer design with the Fellgett's advantage is analyzed. The design enables sub-nm spectral resolution on a millimeter-sized, fully packaged chip without moving parts., National Science Foundation (U.S.) (Award 1506605), United States. Department of Energy (Grant DE-NA0002509)

Solution-based electrospray film deposition, which is compatible with continuous, roll-to-roll processing, is applied to chalcogenide glasses. Two chalcogenide compositions are demonstrated: Ge[subscript 23]Sb[subscript 7]S[subscript 70] and As[subscript 40]S[subscript 60] , which have both been studied extensively for planar mid-infrared (midIR) microphotonic devices. In this approach, uniform thickness films are fabricated through the use of computer numerical controlled (CNC) motion. Chalcogenide glass (ChG) is written over the substrate by a single nozzle along a serpentine path. Films were subjected to a series of heat treatments between 100 °C and 200 °C under vacuum to drive off residual solvent and densify the films. Based on transmission Fourier transform infrared (FTIR) spectroscopy and surface roughness measurements, both compositions were found to be suitable for the fabrication of planar devices operating in the mid-IR region. Residual solvent removal was found to be much quicker for the As[subscript 40]S[subscript 60] film as compared to Ge[subscript 23]Sb[subscript 7]S[subscript 70]. Based on the advantages of electrospray, direct printing of a gradient refractive index (GRIN) mid-IR transparent coating is envisioned, given the difference in refractive index of the two compositions in this study., United States. Defense Threat Reduction Agency (Contracts HDTRA1-10-1-0073 and HDTRA1-13-1-0001)

Computational mechanics and glass science have been applied to the study of precision glass molding (PGM). Early in the study a coupled thermo-mechanical finite element model was rigorously validated and then used in a detailed sensitivity analysis to identify important material and process behaviors. This experience led to a detailed investigation to characterize friction and determine viscosity in the important range of 107.5 109 Pa*s. Viscosity is the primary behavior that allows shape change in glass forming processes and as such must be characterized very accurately. Furthermore, in the viscosity range of interest friction complicates approaches used to obtain viscosity such as parallel plate viscometry. In addition stress relaxation was identified as a very difficult behavior to characterize and a special no-slip glass specimen was designed to obtain it. The most important behavior revealed in the sensitivity analysis was structural relaxation, the characterization of which was a focus in the last year of the project. In addition extensive work was done developing analytical processes to evaluate mold tooling-glass material interaction tendencies in PGM. This provides the know-how needed in both research and development to successfully refine the PGM process through both computational mechanics and glass science.

This paper reviews ongoing progress in the development of novel on-chip planar molecular sensors in infrared-transparent chalcogenide glasses. We demonstrate on-chip cavity-enhanced refractometry and infrared absorption spectroscopy for sensitive detection of proteins and small molecules.

In this work, we demonstrate the controlled synthesis of silica nanoparticles as small as 30 nm (+/- 5 nm) and as large as 250 nm (+/-30 nm) in minutes using surfactant free, microwave-assisted synthetic techniques. Proper choice of solvent, silicic acid precursor, catalyst, and microwave irradiation time were the variables used to control nanoparticle size and, ultimately, overcome the previously reported shortcomings of using microwaves for silica nanoparticle synthesis. In these reactions acetone, a low-tan delta solvent, mediates the condensation reaction, while selective absorption of pulsed microwave radiation by the precursor promotes nanoparticle growth. Dynamic light scattering data, scanning electron micrographs, and transmission electron micrographs of the reaction products show that the size, shape, and granularity of the silica nanoparticles are highly dependent on reaction conditions. These microwave methods have utility for mass production of silica nanoparticles or other nanoparticles by flow-through microwave synthetic methods for industrial applications, as well as a facile method for encapsulating or embedding materials with silica for improved functionality and stability., The original document contains color images. Prepared in collaboration with the Oak Ridge Institute for Science and Education, Belcamp, MD, and the School of Materials Science and Engineering, Clemson University, Clemson, SC. Sponsored in part by DTRA.

Characterization of polymers during polymerization is a challenge. Especially difficult is to study kinetics of gel formation inside tiny droplets. In many cases, viscosity of these fluids increases exponentially fast. In this paper, the rheological properties of fluids were evaluated by examining the behavior of magnetic nanorods in rotating magnetic field. We proposed a theory describing the rotation of a magnetic nanorod in a fluid when its viscosity increases with time exponentially fast. To confirm the theory, we studied the rheology of poly(2-hydroxyethyl-methacrylate) (HEMA)-based hydrogel undergoing photopolymerization and cross-linking with diethylene dlycol dimethacylate (DEGDMA). We showed that magnetic rotational spectroscopy provides rich physico-chemical information about the gelation process. . . . . Remarkably, one can analyze not only the liquid state of the polymer, but the gel as well. Since the probing nanorods are measured in nanometers, this method can be used for the in vivo mapping of the rheological properties of biofluids and polymers on a microscopic level at short time intervals when other methods fail short., The original document contains color images. Prepared in collaboration with the School of Materials Science and Engineering, Clemson University, Clemson, SC. Published in Langmuir, v28 n26 p10064-10071, 2012.

Electrical and thermal conductivity of materials are typically correlated, while some applications, including thermoelectrics, require these parameters to be controlled independently. Such independent control of thermal and electromagnetic properties can be achieved by using nanocomposites. In this study, nanocomposites were produced by mixing a small amount of carbon nanofibers (CNF), Carbon coated Cobalt (Co), and nickel nanowires (NiNW) with paraffin, which has low thermal and almost zero electrical conductivity. The fraction of nanoinclusions in the paraffin matrix was very low (below 1%),. We showed that the thermal properties of nanocomposites are essentially the same as those of pure paraffin, while electromagnetic properties are significantly different. To determine the dependence of the heating rate on filler concentration, paraffin-based samples were heated in the microwave oven. We found that the heating rate of nanocomposites made of carbon nanofibers is much greater than that of any other nanocomposites. These findings suggest that at 2.45 GHz frequency, the heating rate is mostly controlled by the electrical losses in the fillers. The theoretical model predicts that the heating rate increases linearly with the particle concentration, which is in agreement with the experimental data., The original document contains color images. Prepared in collaboration with the School of Materials Science and Engineering, Clemson University, Clemson, SC.

Current methods of reducing physiological strain on a soldier wearing armor vest need significant improvement. To this end, the major objective of this work was to conduct research on development of effective lightweight evaporative cooling system capable of delivering significant cooling effect without or with minimal power requirements and additional weight load. During the project we developed major methodology and equipment to measure cooling power and temperature effect of virtually any cooling system arrangements in laboratory conditions reliably. Resultantly, Surface Differential Scanning Calorimeter (SDSC) was created. In addition, we design and test a novel autonomous evaporative cooling system. As a result of the work several cooling arrangements utilizing an evaporative cooling mechanism were created. The driving force enabling significant evaporation is the temperature difference between parts of the arrangement created by cooling metal foil located on the outside of the vest. The best system demonstrated cooling power of about 100 W/m2 and surface cooling effect of 7-8 oC without using any external power source. The system is extremely lightweight, compact and self-sufficient. We also developed the procedure for preparation of hydrophobic membrane assembly and large hydrophobic-hydrophilic gradient fabric for directional water transport inside of the cooling system.

In this paper, we review the design, processing, and characterization of novel planar infrared chemical sensors. Chalcogenide glasses are identified as the material of choice for sensing given their wide infrared transparency as well as almost unlimited capacity for composition alloying and property tailoring. Three generations of on-chip spectroscopic chemical sensor devices we have developed: waveguide evanescent sensors, micro-disk cavity-enhanced sensors and micro-cavity photothermal sensors are discussed., United States. Dept. of Energy (award number DE-SC52-06NA27341)

A monolayer of thermoresponsive microgel nanoparticles, containing poly(N-isopropylacrylamide) (PNIPAM), has been anchored to the surface of silicon wafers, glass slides, polyvinylidene fluoride (PVDF) fibers, and tungsten wires using a grafting to approach. The behavior of the synthesized grafted layers is compared with the behavior of the PNIPAM brushes (densely end-grafted layers). The comparison demonstrates that in many aspects the microgel grafted layer is comparable to PNIPAM brushes with respect to its thermoresponsive properties. Indeed, the grafted monolayer swells and collapses reversibly at temperatures below and above the lower critical solution temperature (LCST) of PNIPAM. For the flat silicon substrate, a wettability study of the grafted layer shows an approximately 20 deg increase in the advancing contact angle of water upon heating above the LCST of PNIPAM. Wettability data obtained for the tungsten wires indicate that the grafted microgel layer retains its ability to undergo morphological changes when exposed to external temperature variations on complex curved surfaces. Therefore, the microgel-grafted layer can be considered as a system capable of competing with the PNIPAM brushes., Prepared in cooperation with Clemson University, Clemson, SC. Published in Soft Matter, p9962-9971, 2011.

Current methods of decontaminating Chemical Warfare Agents (CWA) contaminated equipment need significant improvement. To this end, the major objective of this work was to conduct research on development of effective nano and micro structured composite coatings capable to collect and decontaminate the chemical agents. In addition, the coating is intended to minimize the contamination cross-section of a coated vehicle. During the project we developed major components required to build effective protecting coatings against CWA. As a result of the work conducted several types of low-surface-energy coatings were created.