New electrically powered microscopic motors, no larger than the width of a human hair, have potential applications in the next few years in both medical and microsurgical equipment and scientific instruments. Bell Labs and the University of California, Berkeley, reported on the new process at the same time, but Berkeley holds a patent on the process, which uses the techniques and materials of semiconductor manufacturing. The rotor in the motor is about two-thousandths of an inch in diameter. Its teeth, or rotor poles, an each about the size of a red blood cell. The whole motor is about three-thousandths of an inch across. Integrated with microelectronics, micromachines could be employed as miniature assembly-line tools, or as new instruments for intricate surgery and delicate laboratory manipulation. Says developer Richard S. Muller professor of electrical engineering and computer sciences at Berkeley, "Today's microprocessors provide silicon 'brainpower.' The coming revolution will couple these with silicon 'muscle' at the same scale."
New Technique Monitors Actinides
The first technique sensitive enough to monitor the chemistry of radioactive compounds in groundwater at temperatures expected in a nuclear waste repository has been developed by the Department of Energy's Argonne National Laboratory. The technique, laser photoacoustic spectroscopy (LPAS), is 1,000 times more sensitive than other spectroscopic techniques currently used to determine the chemistry of actinides in groundwater. A laser fires a light beam of a single wavelength simultaneously at two samples of water—one without actinide and one with the unknown actinide level. Molecules in the samples absorb laser energy, then give it back as heat. The heat causes each sample to expand, producing a pulse of sound that is detected by sensitive microphones. The pulse from the sample containing no actinide is subtracted from that of the sample containing actinide, resulting in a pulse for the actinide alone.
Microscope Uses Reflection Geometry
University of Michigan physicists have built the first positron reemission microscope that uses reflection geometry to image a variety of targets in minute detail. The microscope uses positrons, the antimatter counterpart of electrons, to cause an image to be formed on a video screen. The sample surface absorbs some of the positrons and re-emits the remaining positrons, which diffuse either to the side on which they are incident (reflection geometry) or straight through (transmission geometry). In either case, the incident high-energy positrons are re-emitted as slow positrons, accelerated and focused through standard electron optics lenses. The microscope holds possibilities for investigating surface atom diffusion and surface diffusion of defects in a variety of materials including computer chips and semiconductors.
