Technology Bulletin 1305

Solid-state switch may be key to robots with a human-like brain

Ever since the first science fiction novel appeared in book stores, human-like robots have haunted our imaginations. An electronic, solid-state neural switch developed by researchers at Raytheon Systems and the University of Texas at Dallas may transform such a creature from fiction to non-fiction. Principal researcher Larry Cauller, a neuroscientist at the University of Texas, and Andrew Penz of Raytheon have developed nanoelectronic processors, which they say can act like neurons in a human brain. These gallium-arsenide processors feature layers thin enough to allow electrons to fan out or "tunnel" in many directions, making each electron stream behave as if it was inside a one-way device such as a diode. Increasing numbers of electrons pass through the same channel until their motion becomes inhibited by their own electric fields. Electron numbers then drop until the field dissipates, and the process begins again. The tunneling pattern forms an N-shaped curve, which the team says is remarkably similar to that displayed by the sodium and potassium ion channels in nerve cells. Cauller and Penz's computer simulations show that devices like this could transmit signals similar to a pulse from a nerve cell. By placing thousands of these nano-sized processors, called resonant tunneling diodes (RTDs), on one chip, Cauller expects to build an artificial brain. The two-way connections between this brain's cortex and the environment allow it to observe the results of its own actions, potentially giving it the power to learn and anticipate. The researchers hope to have it start learning from environmental stimuli early next spring. E-mail [email protected].

'Smart' antennas promise better satellite images

Satellite antennas may soon self-adjust, with a little help from smart materials. Presently, satellites move the entire mechanism beneath an antenna to change its direction. This creates inertial forces that throw off the satellite's orientation. Gregory Washington, assistant professor of mechanical engineering, and Hwan-Sik Yoon, a graduate student from Ohio State University (Columbus, OH), discovered a way to build self-adjusting antennas. "An adjustable antenna can make fine movements on its own, like we do when we look around with our eyes," says Washington. Because its actuators are made of light materials, such as plastic and piezoceramics, very little inertia would be generated. Scientists knew that adjustable antenna reflectors made of plastic were light enough for space, but they were too flexible to afford good control. Through computer simulations with a modified POMESH (Physical Optics Mesh), a computer code developed at the Jet Propulsion Laboratory (Pasadena, CA), Washington and Yoon proved that thin piezoceramic patches spaced around the back of a reflector will reinforce the plastic while controlling its shape. "When we attach this material to another surface and it expands, the surface bends," Washington explains. "When it contracts, the surface bends the other way. With that movement, we can change the overall shape of a structure." In the case of the antenna, the change alters the properties of the reflector or the antenna itself. Washington and Yoon found that the plastic reflector materials must be molded to a particular shape and the actuators bonded to the structure at specific temperatures and pressures for the design to work. They hope to have a prototype ready by March for field testing by NASA. E-mail [email protected].

Layered materials result in powerful new laser

By developing a new material, scientists at Bell Labs (Murray Hill, NJ) have demonstrated "the first semiconductor laser that simultaneously emits light at multiple, widely separated wavelengths." The experimental light source does the work of three conventional semiconductor lasers--with a hundred times more power. Possible applications include: pollution and environmental monitoring, industrial process control, and combustion and medical diagnostics. Federico Capasso, head of the lab's Semiconductor Physics Research Department, says: "The key breakthrough in this development was the design and synthesis of a new laser material consisting of tens of layers of elements, each five to 20 atoms thick. By precisely tailoring the layers' thickness we created an artificial material in which electrons have energy levels that emit light at several pre-selected wavelengths." In operation, an electric current is injected into the device and electrons cascade through 25 stages of the new material, emitting laser photons at two or three wavelengths in each stage. This cascade boosts the power of the laser to a peak power of 100 mW at wavelengths of 6.6 and 8.0 microns. The laser differs from conventional semiconductor lasers used in fiber-optic communications and compact disc players by using quantum engineering of the electronic energy levels in materials to produce the lasers. The wavelength is entirely determined by the thickness of the active layers rather than by the chemical composition of the material. This permits a huge wavelength region to be covered using the same material, and multiple wavelengths to be simultaneously emitted by a single laser. Phone (908) 582-3000.

Material scientists get a 'springy' look at composites

For years, material scientists wanted a direct way to gauge the nanoscopic elastic, or "springy" properties of materials in order to determine their mechanical behaviors, particularly at the "joins" of composites. The wait may soon be over. Scientists at Oxford University (Oxford, England) reported in Materials World on the development of the Ultrasonic Force Microscope (UFM). The UFM is a combination of two microscopy techniques: acoustic microscopy and its sensitivity to elastic properties, with atomic force microscopy. The UFM technique uses a high frequency ultrasonic vibration to shake the material being tested. The atomic force microscope provides the nanoscale resolution, while the acoustic microscope measures the "bounce" of the material. Differences in the vibrations characterize the elastic properties of many types of material, such as the fibers and the plastic matrix in a composite. This technique, say the researchers, can detect cracks or delaminations present because these will interrupt the propagation of acoustic waves through the material. E-mail [email protected].

Data acquisition in the palm of your hand

For the first time 3Com's Palm Pilot, a personal digital assistant (PDA), can be a multi-channel handheld data acquisition system, says Steve Sabram, president of Datastick Systems (Campbell, CA). Datastick developed the hardware to snap the data-acquisition device onto the modem connector of the Palm III PDA or the PalmPilot Professional Edition. The hardware provides a multi-channel port for field measurement and logging concurrently, in real time, from up to six analog sensing units. The company also wrote the software to provide full analog to digital conversion for personal digital systems. The handheld device operates anywhere a laptop proves cumbersome, says Sabram. The Datastick data logger measures, records, and displays 3D magnetism, 3D acceleration, temperature, pressure, and many other analog sensor applications. For the first time on the Palm Computing Platform, Sabram adds, users can compensate for a sensor package's non-linear sensor response curve by custom-editing conversion functions and viewing real-world, linear readings. Datastick Systems expects shipments during the first quarter of 1999. Applications include: environmental, industrial, and safety monitoring. E-mail: [email protected].

Old tires get a new lease on life

Ever wonder what happens to those worn tires you throw out at the end of 50,000-plus miles? Researchers at the University of Illinois and the Illinois State Geological Survey (Champaign, IL) recycle them into activated-carbon adsorbents for air-quality control applications. "In the U.S. alone, more than 200 million tires are disposed of annually," notes Mark Rood, a University of Illinois professor of environmental engineering and one of the co-investigators on the project. "These waste tires can serve as an inexpensive and plentiful feedstock for carbon adsorbents that have commercial value in gas separation, storage, and cleanup applications." In a collaborative research program between the university and the State Geological Survey, Rood, engineer Massoud Rostam-Abadi, and graduate student Christopher Lehmann compared the performance of carbon adsorbents derived from shredded tires with the performance of existing commercial products. They also characterized the physical properties--such as pore size--of the adsorbents and studied the surface chemistry that can influence adsorption. The tests showed tire-activated carbon performed as well or better than some commercial carbons. "The next step is to produce enough quantities of tire-derived activated carbon for pilot-scale testing to show that this material works under actual industrial test conditions," Rostam-Abadi says. Potential commercial applications include: removal of toxic pollutants from fossil-fuel-fired power plants, storage of alternative fuels such as natural gas in vehicles, and the removal of volatile organic compounds from industrial-gas streams. E-mail [email protected].

Device heats up blood vessels after surgery

In response to anesthesia, cool temperatures, and paper-thin hospital gowns, many surgical patients experience a drop in core body temperature. To hasten recovery time, researchers at Stanford University developed the Thermo-STAT--an acrylic sleeve and mitt that fits over the hand and seals around the patient's forearm. The device contains a water-perfusion blanket that supplies heat, and is hooked to a vacuum pump to reduce the air pressure inside the sleeve. The Thermo-STAT works on the principle that the hand and bottom of the forearm contain blood vessels specially designed for temperature regulation. A drop in the body's internal temperature automatically shuts down blood flow through these heat-exchange blood vessels to prevent more heat from escaping. This may help a person survive in some conditions, but it also makes the warming process slower and more difficult. The Thermo-STAT reverses this shutdown, called vasoconstriction, by slightly reducing the air pressure within the sleeve. The reduced pressure causes the vessels to open and blood to flow normally. Aquarius Medical Corp. (Scottsdale, AZ) has licensed the patented design. E-mail: [email protected].