(2 of 3)
Human interest in tiny machines dates back to the clockwork toys of the 16th century. But it was not until this century that making things smaller became a matter of military and economic survival. Spurred by the cold war and the space race, U.S. scientists in the late 1950s began a drive to shrink the electronics necessary to guide missiles, creating lightweight devices for easy launch into space. It was the Japanese, though, who saw the value of applying miniature technology to the consumer market. In his book Made in Japan, Akio Morita tells how he proudly showed Sony's $29.95 transistor radio to U.S. retailers in 1955 and was repeatedly asked, as he made the rounds of New York City's electronics outlets, "Who needs these tiny things?"
American manufacturers eventually learned what the Japanese already knew: that new markets can be created by making things smaller and lighter. (The popular phrase in Japan is kei-haku-tan-sho -- light, thin, short and small.) Ten years ago, Black & Decker scored big when it shrank the household vacuum cleaner from a bulky 11.2 kg (30 lbs.) to a 0.75-kg (2-lb.) device dubbed the Dustbuster. Tandy and Apple Computers put the power of a room-size computer into something resembling a television-typewriter and created an industry worth $75 billion a year.
Now these breakthrough products look hopelessly oversize. Last month Compaq unveiled a 2.2-kg (6-lb.) full-powered portable computer that fits in a briefcase. Sharp and Poqet make even smaller models that slip into a suit pocket. Today there are fax machines, radar detectors, electronic dictionaries, cellular telephones, color televisions, even videotape recorders that fit comfortably in the palm of a hand.
With the advent of silicon gears, springs and cantilevers, machines will become smaller still. These miniature moving parts can be etched on silicon using a variation on the photolithographic technique used to make computer chips. To build a tiny rotating arm, for example, layers of polysilicon and a type of glass that can be removed with acid are deposited on a silicon base. A hole for the hub is lined with the glass and then filled with polysilicon. When the glass is etched away, the hub remains and the arm is free to spin around its axis.
Sensors like those made by Delco were the first to combine microelectronics and micromachines on one chip. The typical microsensor is a thin silicon diaphragm studded with resistors. Because the electrical resistance of silicon crystals changes when they are bent, the slightest stress on the diaphragm can be registered by the resistors and amplified by electronic circuits.
As prices drop, these devices will become ubiquitous. By 1995 the typical car may contain as many as 50 silicon sensors programmed to control antilock brakes, monitor engine knock and trigger the release of safety air bags. Similar sensors are already employed in the space shuttle Discovery to measure cabin and hydraulic pressures and gauge performance at more than 250 separate points in the craft's main engines.