Tech Briefs

Flexible Biohybrid Nanomembranes for Multifunctional Sensors

A document describes recent activities in a continuing effort to develop devices, based on biohybrid nanomembranes, that would perform diverse sensory functions. The term "biohybrid nanomembranes" signifies flexible organic/inorganic composite membranes, of the order of tens of nanometers thick, typically comprising polymeric outer supporting layers and wholly or partly inorganic (e.g., biomineralized) inner sensory layers. This development is envisioned to yield novel acoustic, infrared, and photothermal sensors characterized by extreme degrees of miniaturization and sensitivity. The main focus of recent activities was on (1) synthesis of new branched and peptide-containing molecules to be incorporated into membranes and (2) further development of sophisticated freely standing membranes with micropatterned structures. In addition, membranes encapsulating arrays of carbon nanotubes and gold nanoparticles were fabricated and tested in micromechanical Raman-spectroscopic studies. Recent findings include the following:

Flexible nanomembranes with encapsulated silver nanowires and semiconducting quantum dots exhibit outstanding micromechanical, fluorescence, and conducting properties. Quantum-dot nanomembranes suspended over optical cavities exhibit exceptional backlight enhanced fluorescence intensity. Multifunctional hyperbranched molecules control the growth of monolayers of monodisperse silver nanoparticles at air-water interfaces. Silver-reducing peptides can be encapsulated in ultrathin polymer films and there utilized to effect formation of silver nanoparticles.
Posted in: Briefs, Materials
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Detecting Explosives by Use of LIBS

Laser-induced breakdown spectros - copy (LIBS) has been investigated for potential utility as a means of detecting trace amounts of chemical explosives and residues thereof in lawenforcement, forensic analysis, and military settings. In LIBS (see figure), a laser is used to rapidly generate a microplasma of a sample, and the light emitted by the microplasma is analyzed to identify (and determine the intensities of) spectral lines of elements and compounds in the sample. In previous applications for purposes other than detection of explosives, LIBS has been shown to enable remote, rapid, multielement micro-analysis of bulk samples (solid, liquid, gas, aerosol) of compounds having concentrations in the parts-per-million range.

Posted in: Briefs, Physical Sciences, Lasers, Spectroscopy, Chemicals, Hazards and emergency management, Rescue and emergency vehicles and equipment
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NO-Generating Coats for Subcutaneous Glucose Sensors

In a research program now in progress, polymeric materials that catalyze the generation of nitric oxide (NO) at low concentrations are being developed and tested for utility as coatings on surgically implantable amperometric glucose sensors. Heretofore, efforts to develop subcutaneous sensors for real-time clinical monitoring of glucose concentrations in diabetic patients have been stymied by inflammatory/foreign-body responses to implantation of sensors. The present research program follows from an observation, made in a related prior research program, that local generation of NO at low concentrations enhances the biocompatibility of implanted sensors by reducing inflammatory responses.

Posted in: Briefs, Medical, Sensors and actuators, Nitrogen oxides, Prostheses and implants, Coatings Colorants and Finishes
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Fusion of Image- and Inertial-Sensor Data for Navigation

Amethod of real-time fusion of readout data from electronic inertial and image sensors for passive navigation has been developed. By "passive navigation" is meant navigation without the help of radar signals, Lidar signals, Global Positioning System (GPS) signals, or any other signals generated by on-board or external equipment. The concept of fusion of image- and inertial- sensor data for passive navigation is inspired by biological examples, including those of bees, migratory birds, and humans, all of which utilize inertial and imaging sensory modalities to pick out landmarks and navigate from landmark to landmark with relative ease. The present method is suitable for use in a variety of environments, including urban canyons and interiors of buildings, where GPS signals and other navigation signals are often unavailable or corrupted.

Posted in: Briefs, Information Technology, Mathematical models, Navigation and guidance systems, Data management
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MEMS Offset-Beam Torsional Electrothermal Actuators

Prototypes of microelectromechanical system (MEMS) rotational actuators based on a principle of torsion induced by thermal expansion of electrically heated offset beams have been designed, fabricated, and tested. It is envisioned that after further development, these actuators might be used to satisfy stringent competing requirements for smaller, larger-force, largerdisplacement actuators in increasingly complex MEMS systems. Until now, MEMS thermal actuators have been regarded as inefficient and capable of producing, variously, either large forces and small displacements or small forces and large displacements. The actuators of the present type are intended to overcome some of the deficiencies heretofore attributed to MEMS thermal actuators by producing medium displacements and medium forces.

Posted in: Briefs, Mechanical Components, Microelectricmechanical device, Sensors and actuators
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Update on Implantable Sensors for Metabolic Monitoring

Progress has been made in a continuing effort to develop surgically implantable, biocompatible electrochemical- sensor arrays for continuous measurement of concentrations of analytes that play major roles in human and animal metabolism. This development at an earlier stage was described in "Implantable Electrochemical Sensors for Metabolic Monitoring" (ARL-0017), Defense Tech Briefs, Vol. 1, No. 4 (August 2007), page 28. To recapitulate: in the electrochemical-monitoring approach followed in this development effort, cyclic voltammetry, amperometry, squarewave voltammetry, or a combination of these techniques is used to measure the rate of catalytic oxidation of glucose by the enzyme glucose oxidase (GOX) in a reaction mediated by poly[vinyl pyridine Os(bipyridine)2Cl]- co-ethylamine (POs- EA), which is an osmium-based polycationic redox polymer. To ensure biocompatibility, the GOX is entrapped in a poly(ethylene glycol) diacrylate (PEGDA) hydrogel that has previously been demonstrated to be biocompatible.

Posted in: Briefs, Medical, Architecture, Biological sciences, Prostheses and implants, Polymers
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Use of a Heat Pipe to Cool Aircraft Electronics

The first steps have been taken in a continuing project to study the suitability of dissipating heat from electronic and electric-actuator equipment aboard an aircraft by using a loop heat pipe, containing water as the working fluid, that delivers the heat to the exterior aircraft skin. The first steps include the following:

Posted in: Briefs, Electronics & Computers, Avionics, Water, Cooling, Hoses
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Microscale Electrical Contacts for Self-Assembly

An experimental study of self-assembly processes in which small, heterogeneous components become spontaneously aligned with each other and bonded through soldering of mating electrical contacts was performed to determine and, to the extent possible, to extend the lower limits of, contact sizes for which such processes can be utilized successfully. The issue of self-assembly arises because advances in microelectronic circuitry and microelectromechanical systems pose significant challenges in the construction of threedimensional structures and the building of integrated systems made of parts from incompatible microfabrication processes. Although robotic “pick-and-place” techniques are now used to integrate parts made by different processes, the ability to efficiently handle individual parts diminishes as their sizes decrease below about 300 μm. Self-assembly is attractive as an alternative means of integrating smaller parts into structures.

Posted in: Briefs, Electronics & Computers, Microelectricmechanical device, Assembling, Joining
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Electrical Filters Containing Multistage PBG Resonators

Electrical filters of a recently invented type are designed and constructed as transmission lines into which multistage photonic-band-gap (PBG) structures are incorporated. As used here, "transmission lines" refers to any or all of the standard electrical media, including coaxial cables, microstrips, and the like, used for propagation of electromagnetic waves along enclosed or well defined paths. The term "electrical filters" is used here in a conventional sense, denoting any of a variety of systems or components that block propagation of signals in certain frequency bands (stop bands) and/or support propagation in other frequency bands (pass bands). The PBG structures used in this invention can be any of a variety of dielectric or electrically conductive structures, containing precise periodic or quasiperiodic arrays of holes or other features that can be tailored to obtain desired stop bands.

Posted in: Briefs, Photonics, Amplifiers, Architecture, Conductivity
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BC VCSELs for RF/Photonic Links

Bipolar cascade (BC) vertical-cavity surface emitting lasers (VCSELs) of a type intended specifically for use in radio-frequency (RF)/photonic links have been demonstrated. As used here, "RF/photonic link" signifies a communication link in which, at the transmitter, the continuous-wave output of a laser is modulated with an RF (typically, a microwave) signal and the resulting modulated laser beam is conveyed via free space or an optical fiber to a receiver, where the RF signal is detected. RF/photonic links offer advantages for short-range, wide-band communications and for diverse functions involved in phased arraying of large microwave antennas.

Posted in: Briefs, Photonics, Antennas, Fiber optics, Lidar, Wireless communication systems
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Effect of Laser Noise on an Analog RF/Photonic Link

Aset of equations has been formulated to enable quantification of several aspects of the performance of an analog photonic communication link as affected by laser noise. A procedure for measuring the laser noise has been devised to provide laser-noise data for use in the equations. The equations and procedure are generally applicable to diverse analog photonic links, in the design and operation of which laser noise is of great concern. Analog photonic links have been found to be useful as subsystems, radio-antenna-arraying systems, optoelectronic oscillators, and wide-band signal-processors.

Posted in: Briefs, Photonics, Finite element analysis, Lasers, Noise measurement
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C++ Architecture for Simulating UAVs

A conference paper describes the use of the CADAC++ software system for simulating operations of uninhabited aerial vehicles (UAVs) in conjunction with moving ground targets while interacting with other UAVs and with satellites that assist in targeting. CADAC++ was developed by rewriting the prior Fortran-language CADAC software to take advantage of features of C++ that enable multiple instantiation of UAVs, targets, and satellites, thereby enabling the study of such phenomena as fly-out trajectories, third-party targeting, and distributed information sharing. [CADAC (Com puter Aided Design of Aerospace Con cepts) is chiefly an engineering tool to aid in developing aerospace vehicles.] The architecture of CADAC++ is based on the hierarchical structure of inherited classes, wherein, among other things, every instantiated vehicle object is encapsulated with its methods and data. The paper discusses this architecture in more detail, outlining its class structure and a global data bus through which encapsulated vehicle-objects communicate. The paper then discusses a simulation involving a generic UAV model having five degrees of freedom in order to demonstrate the interactive features of the simulation and to support the conclusion that C++ is the programming environment of choice for networked simulations.

Posted in: Briefs, Information Technology, Computer simulation, Satellites, Unmanned aerial vehicles
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Overcoming Obstacles to DoD Software Technology Transition

The term "Software Wind Tunnel" (SWiT) denotes an institution proposed to be established as a means of overcoming obstacles that, heretofore, have impeded technology transition in connection with research on, and development and utilization of, software needed for software- intensive systems of the Department of Defense (DoD). The term "technology transition" should not be confused with the term "technology transfer," which denotes a process in which an item of technology developed by or for the government is transferred to industry (usually) or vice versa. Instead, "technology transition" denotes a process in which an item of technology is made to evolve from its developmental form into a mature form and in which that item is adopted by its intended end users.

Posted in: Briefs, Information Technology
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Magneto-Fluid Dynamics Calculations for Aerodynamics

Governing differential equations, and algorithms to solve the equations numerically, have been developed to enable computational simulation of weakly ionized aerodynamic flows in the presence of electromagnetic fields. The equations and algorithms are intended mainly for application to airflows about, and within the engines of, contemplated hypersonic vehicles. There, strong imposed magnetic fields and perhaps imposed electric fields might be used, variously, for reducing transfer of heat to solid surfaces, for extracting electric energy from flows, or for accelerating or decelerating flows to enhance combustion of fuel or otherwise increase energy efficiency.

Posted in: Briefs, Information Technology
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GOx/CNT/Silica Composites for Bioelectrodes

Composites of glucose oxidase (GOx), carbon nanotubes (CNTs), and biologically synthesized silica have been synthesized and tested. These composites are prototypes of biological/electrical interfacial materials and could enable the development of the next generation of devices for a variety of medical, scientific, industrial, and military applications. In particular, it is envisioned that materials based on these prototypes will be integrated into bioelectrodes for biosensors and biofuel cells.

Posted in: Briefs, Materials, Biomaterials, Composite materials, Materials properties, Nanotechnology
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Planning Observations by Unmanned Surface Vessels

Three algorithms, and software that implements the algorithms, have been conceived and analyzed as means of effecting automated planning of scientific observations by a fleet of unmanned surface vessels (USVs) equipped with sensors and operating over a large and possibly changing ocean area. Typical observations envisioned in the development of these algorithms include water-temperature measurements ahead of the path of a hurricane (see figure) and fluorometer readings to track harmful algal blooms.

Posted in: Briefs, Information Technology
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Progress in Design and Synthesis of Nanostructured Materials

A five-and-a-half-year integrated multidisciplinary research project has been characterized by three themes pertinent to the development of advanced materials having tailorable microstructures and/or nanostructures. These themes are (1) biocompatible nanolithographic methods of patterning and templating of materials to have two- and three-dimensional nanostructures; (2) nucleic-acid-based approaches to preparing (both in solution and from predesigned, nanostructured surface templates) supramolecular structures tailored to perform specific functions; and (3) protein-based or inspired molecular and supramolecular architectures. The contributions of this and other related research projects can be expected to lead to the development of diverse nanostructured organic and inorganic materials and structures, including catalytic peptide tubes, hostguest materials for molecular separations, quantum-dot and magnetic-particle arrays, bio-nanoelectronic circuitry, photonicbandgap and three-dimensional electronic power structures, and novel biowarfare- detection materials.

Posted in: Briefs, Materials, Research and development, Fabrication, Nanomaterials, Nanotechnology
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Mixing and Combustion in Turbulent, High-Speed Flows

A collection of reports presents a detailed description of a research program that focused on fundamental investigations of mixing and combustion in turbulent subsonic and supersonic flows like those encountered in high-speed air-breathing aircraft engines. The research included close coordination of effort between experiments and numerical simulations. Recent advances in instrumentation, including some made as part of this program, were utilized in the experiments. The research has been responsible for significant progress in the understanding of molecular mixing in high-speed flows in complicated geometries relevant to scramjet combustors and to high-speed aircraft engines in general. The research included a study oriented toward improving predictions of hydrocarbon flames in such flows and understanding the requirements for combustion of hydrocarbons and holding flames. The study involved comparisons of detailed experiments and detailed predictions of phenomena in stagnation-flame environments that replicate the fundamental effects that influence the stability and extinction of flames. An investigation of the three-dimensional structure of scalar dispersion, with a focus on grid turbulence, has been started and already has yielded new information with relevance to applications of turbulent mixing, including non-premixed combustion and dispersion of pollutants.

Posted in: Briefs, Physical Sciences
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Microcompression Tests of a BMG and a Tungsten/BMG Composite

Uniaxial-compression tests of micron-scale specimens (microcompression tests) of a bulk metallic glass (BMG) and of a tungsten/BMG composite have been performed to contribute to understanding of size-dependent mechanical properties of these and other, similar materials. There is increasing interest in fabricating micro- electromechanical systems from BMGs, and in fabricating kinetic-energy (ballistic) penetrators from BMGs and tungsten/ BMG composites. While the mechanical properties and deformation mechanisms of macroscopic, monolithic BMGs in bulk form are generally well understood, these properties are not necessarily equivalent for the BMG alloys cast in composite form or for micron-scale specimens. In a tungsten/BMG composite, dissolution of tungsten in the BMG matrix frequently manifests itself in the formation of complex crystalline phases and the concomitant decrease in the overall amorphous content of the matrix. Hence, it becomes important to compare the properties and deformation mechanisms of the monolithic BMG with those of the BMG as found in the composite accompanied by other phases and heterogeneities.

Posted in: Briefs, Physical Sciences
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Kinetic Modeling of Laser-Induced D-T Fusion

A computational- simulation study was performed to assess the feasibility of laser-induced fusion of deuterium nuclei with tritium nuclei as a means of generating neutrons for use in neutron radiography. [D-T fusion reactions produce α particles (He nuclei) plus the desired neutrons.] As in prior studies of laser-induced D-T fusion, the basic idea is to irradiate a small deuterium-and- tritium-containing target with a brief, intense laser pulse that causes a shock wave to propagate into the target. The shock wave ionizes and accelerates a substantial portion of the D and/or T molecules, resulting in, among other phenomena, collisions between D and T nuclei. The question of feasibility is essentially the question of whether, by use of a realistic target and a realistic laser pulse, a sufficient number of ions could be accelerated to sufficient kinetic energy such that the number of resulting D-T fusion reactions would suffice to produce a radiographically usefully large number of neutrons.

Posted in: Briefs, Materials, Computer simulation, Lasers, Forming, Radiation
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FPGA-Based Communication Channel for Digital Signal Processor Chips

A method for networking, and a network of, digital signal processors (DSP) via at least one field-programmable gate array (FPGA) enables the simultaneous broadcast of data from a DSP to a number of DSPs. The apparatus comprises a host DSP, at least one FPGA in communication with the host DSP for receiving a digital signal from the host DSP, and at least one non-host DSP in communication with at least one FPGA for receiving the digital signal.

Posted in: Briefs, Electronics & Computers, Communication protocols, Integrated circuits, Wireless communication systems
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Applying Reconfigurable Computing to Acoustic Sensors Using FPGAs

A novel microsensor processing architecture allows a field-programmable gate array (FPGA) to act as a reprogrammable preprocessor or coprocessor to a general-purpose processor (GPP). The FPGA does most of the computationally complex pieces of the algorithm, while the GPP is lightly loaded, performing control, communications, and housekeeping tasks (Figure 1). The flexible architecture supports a wide range of low-power applications, while still being able to leverage emerging commercial technology.

Posted in: Briefs, Electronics & Computers
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Delta-Sigma UHF Digital Waveform Generator

A prototype Digital Waveform Generator (DWG) in the ultra-high-frequency (UHF) range uses Delta-Sigma (Δ−Σ) modulation techniques, which permit arbitrary and accurate waveform generation. The DWG meets the demanding and diverse waveform requirements of future radar applications, including linear-FM (LFM) and continuous wave (CW) signals. This DWG also allows for the generation of waveforms at other frequencies by up-conversion or down-conversion.

Posted in: Briefs, Electronics & Computers
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Network-Enabled Resource Devices

Network Enabled Resource Devices (NERDs) combine the most common electronic components used in robotic applications into a standard electronics box with "plug-n-play" capabilities. Risk reduction efforts, systems testing and integration, and modifying the functionality of evolving systems becomes greatly simplified by standardizing core hardware and software components; in many cases, minimal software modifications are required to adapt an existing NERD for an emergent application.

Posted in: Briefs, Electronics & Computers
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Cleaning and Protecting Large Mirrors Using a Polymer Solution

Cleaning and protecting optics is a challenge — contamination must be removed without damaging the surface. Preventing recontamination for extended periods of time after cleaning was unattainable prior to use of polymer strip coat films. The SLRSC Western Range Depot Optics Group, WRDOG, at Vandenberg Air Force Base, is a pioneer in the cleaning and protection of precision glass optics, lenses, and large mirrors using polymer solution technology.

Posted in: Briefs, Photonics, Mirrors, Coatings Colorants and Finishes, Polymers
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Software-Defined Radios for Urban and Indoor Navigation

Software-defined radios (SDRs) are being developed to provide positioning and communication (POSCOMM) services inside buildings and tunnels, under tree canopies, and in other environments in which local radio- communication systems are accessible but Global Positioning System (GPS) signals are not present or are degraded. These SDRs could be especially helpful for teams of first responders (e.g., firefighters), and military personnel operating in urban settings. These SDRs are capable of navigating by use of GPS signals and can switch over to time-of-arrival (TOA) pseudolite navigation when GPS signals become unavailable, provided that signals from suitably placed TOA pseudolite transmitter nodes are available.

Posted in: Briefs, Electronics & Computers
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Conjugated Polymers Having High Charge-Carrier Mobilities

A three-year research project encompassed multiple studies of (1) polymer semiconductors that exhibit relatively high electric-charge- carrier mobilities and (2) applications of these polymers in electronic (including optoelectronic and nanoelectronic) devices. Although these polymers are of broad importance to all polymer semiconductor devices — including light-emitting diodes, photovoltaic cells, photodetectors, and electrophotographic imaging devices — the focus in this project was largely upon the use of these polymers in thin-film transistors, organic light-emitting diodes, and related light-emitting transistors.

Posted in: Briefs, Electronics & Computers
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Incorporating Functional Fillers into Silicone Elastomer Systems

Silicones can be developed into fluids, gels, adhesives, elastomers, and resins designed with unique properties that make them ideal for specific application uses in the defense and aerospace industries. Silicones are most widely known for their ability to maintain elastomeric properties in extreme conditions, but an additional benefit of these materials is the ability to incorporate large amounts of fillers that can impart properties such as electrical and thermal conductivity, and radar-absorbing characteristics. Silicone materials appear in a wide variety of material compositions, and this broad range of material compositions makes silicone a viable option to endless numbers of optic applications.

Posted in: Briefs, Materials, Optics, Composite materials, Elastomers, Materials properties, Silicon alloys
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Gold-Based Nanoparticle Liquids for Electronic Applications

Electrically conductive, solventless nanoparticle liquids, consisting of gold nanoparticles chemically functionalized with large organic molecular groups, have been investigated for potential utility in electronic and electrical applications. These and other solventless nanoparticle liquids, including electrically nonconductive ones, have been topics of recent research directed toward understanding and exploiting their unusual properties. The most obvious unusual property is that a collection of nanoparticles of this type can flow in a liquid-like fashion, notwithstanding the absence of free solvent molecules. By modifying the attractive and repulsive forces between the nanoparticles through modifications of the surface chemistry of the organic ligands, the properties of the resulting nanoparticle liquids can be tailored for specific applications.

Posted in: Briefs, Materials
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Dimensional Stabilization of Composite Space Structures

A research project has yielded progress on several fronts toward the goal of minimizing thermal and aging distortions of composite-material (specifically, polymer- matrix/graphite-fiber) outer-space structures that are required to retain precise dimensions and shapes. The achievements of this project are also applicable to terrestrial composite-material structures to the extent to which various environmental effects can be properly taken into account. Examples include effects of expansion caused by absorption of atmospheric moisture (similar to effects of purely thermal expansion) and effects of outgassing of volatile constituents of polymers (effects of out-gassing are more pronounced in the outer-space vacuum).

Posted in: Briefs, Materials
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