Tech Briefs

Advances in Organic-Based Electronic Devices

A program of research has addressed multiple topics in the field of electronic and optoelectronic devices based on polymers and other organic substances, with special attention to memory devices and solar photovoltaic cells. The accomplishments of this research are summarized as follows:

Posted in: Briefs, Electronics & Computers, Electronic equipment, Research and development, Polymers

AlxInyGa1-x-yN Ultraviolet Light-Emitting Triodes

Light-emitting triodes (LETs) have been the focus of a program of research with a goal of increasing the quantum efficiencies of ultraviolet-lightemitting devices implemented in the AlxInyGa1-x-yN (0 ≤ x+y ≤ 1) material system. Heretofore, AlxInyGa1-x-yN-based light-emitting diodes (LEDs) have exhibited "efficiency droop" — decreasing quantum efficiency with increasing injection current. LETs can be used as means of studying and overcoming efficiency droop.

Posted in: Briefs, Electronics & Computers, Light emitting diodes (LEDs), Performance upgrades

Less-Polluting Resins for Molding Composite Structures

Liquid resins that are suitable for use in molding composite- material structural panels and that contain and emit smaller amounts of air-polluting volatile organic compounds than do corresponding commercial resins have been invented. In particular, these resins are under study as less-polluting potential substitutes for commercial vinyl ester and unsaturated polyester resins heretofore used in making lightweight composite panels for some military vehicles.

Posted in: Briefs, Materials, Volatile organic compounds, Product development, Composite materials, Lightweight materials, Resins, Military vehicles and equipment

Some Advances in High-Temperature Superconductor Coatings

Several advances were made in a program focused on the science and technology of high-temperature superconductors [especially yttrium barium copper oxide ("YBCO")] deposited on normal electrical conductors. This program was part of a continuing effort to develop superconductor-coated normal conductors for use in electric-power systems of interest to the Air Force.

Posted in: Briefs, Materials, Electrical systems, Coatings Colorants and Finishes, Conductivity, Heat resistant materials, Military aircraft, Military vehicles and equipment

The Future of Space Propulsion

A paper presents an overview of state of the art of space propulsion, oriented toward attempting to understand recent history in order to make some predictions about future developments. As used here, "space propulsion" refers generally to what are now called "spacelift" and "spacecraft propulsion." Further, as used here, "spacelift" refers generally to large rockets, associated equipment, and other resources for launching spacecraft into outer space, while "spacecraft propulsion" refers generally only to systems for propelling spacecraft once they are in outer space. The paper includes a summary of recent history of spacecraft propulsion, with greatest emphasis on spacelift systems, from the perspective of striving to maintain the military superiority and economic competitiveness of the United States in the face of the rapid international evolution of space technology. Advantages and disadvantages of various engine designs and propellant substances, and considerations of cost and development time, are discussed. Trends in spacelift (and, to a lesser extent, trends in spacecraft propulsion) are discussed. An attempt is made to predict the general nature of future developments by extrapolating the trends into the foreseeable future.

This work was done by John F. Remen and Glenn Liston of the Air Force Research Laboratory.

Posted in: Briefs, Mechanical Components, Technical reference, Rocket engines, Launch vehicles, Spacecraft

Miniature Wheel-Leg Mobile Robots

Mini-Whegs™ are small mobile robots, designed according to abstracted cockroach locomotion principles, that can run and can climb obstacles taller than themselves. Mini-Whegs are derived from larger mobile robots denoted Whegs™, with modifications to reduce size, reduce the number of mechanisms, and increase relative mobility. The name "Whegs" originated as a contraction of "wheel-legs," referring to three-spoke appendages by means of which these robots move, as described below.

Posted in: Briefs, Mechanical Components, Wheels, Downsizing, Robotics

Progress Toward Carbon-Nanotube Arrays for Probing Cells

Progress has been reported in research oriented toward the goal of fabricating arrays of interconnected single-walled carbon nanotubes (SWNTs) that could serve as probes for measuring localized events within living cells. As used here, "interconnected" signifies mechanically and electrically connected to patterned metal films (interconnections) that lead to contact pads, which, in turn, enable electrical connection to external electronic instrumentation. This research poses a high economic risk because it entails pushing several technological disciplines beyond their present limits. There is no previously reported combination of fabrication techniques and processes for producing carbon nanotubes that have the required properties at the required positions and orientations on patterned metal films.

Posted in: Briefs, Manufacturing & Prototyping, Architecture, Sensors and actuators, Biological sciences, Fabrication, Metals, Nanomaterials