Number 282 (Story #3), August 2, 1996 by Phillip F. Schewe and Ben Stein MICROMECHANICAL SYSTEMS (MEMS) are devices small enough to fit onto a chip. Essentially built with the same lithographic techniques and made from the same semiconductors as other microchips, MEMS fall into two main categories---actuators and sensors. Sensor applications include the use of MEMS as accelerometers for triggering (by detecting the movement of tiny silicon bars on a 3-mm chip) automobile airbags and for measuring blood pressure (using the relative deformation of a 10-micron diaphragm). Mechanical MEMS include micromotors, flaps, and minute steerable mirrors for switching light pulses. Some problems persist (micromotors wear out quickly) but the market for MEMS is expected to be worth billions of dollars by the year 2000. (New Scientist, 29 June.)