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

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

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

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

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

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

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

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

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

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