Technology Circuits

The New York Times

September 23 1999


By Anne Eisenberg

The next time you watch dust motes drifting in the air, consider: Someday the dust motes may be watching you.

Scientists at the University of California at Berkeley are designing tiny airborne devices they call "Smart Dust" that may one day not only observe the likes of lost cats, tornadoes, or even enemy forces but also pass the news along to headquarters, wherever that may be.

The goal of smart dust is to combine sensors, computation and communication in a volume as small as a grain of sand, said its inventor, Kris Pister, a Berkeley professor who is leading the effort to put a complete airborne sensing and communication platform, including power supplys, inside one cubic millimeter.

Dr. Pister hopes that one day his smart dust will be ubiquitous. Grains of it could be used for tasks like monitoring a room's temperature to make sure that people in one side of the room do not freeze while those in the other side bake.

Smart dust may even have a more stealthy purpose.

Joseph Kahn a professor of electrical engineering and computer science at Berkeley who has worked closely on the project with Dr. Pister said he could imagine a future in which microaircraft drop smart dust on the perimeter of a battlefield to measure data like movement of vehicles. Another microaircraft could interrogate the smart dust to find out what it had seen.

There's no need to worry yet about the invasion of privacy by dust motes, or even about inhaling them. Dr Pister's dust grains are still relatively bulky five millimeters on a side, the size of an aspirin, far too heavy to be wafted on air currents.

But Dr. Pister and his group have the individual parts of the system working he said and they have already demonstrated an autonomous. golf ball size sensor that can beam weather information by laser from Coit Tower in San Francisco 10 miles across the bay to Dr. Pister's Berkeley office.

He hopes that the motes will soon be airy enough to float alone sensing and communicating either with a central device or mote to mote.

Dr Pister's smart dust and dozens of other tiny machines are made possible by a technology known as MEMS, short for microelectromechanical systems. MEMS are miniature machines some smaller then a human red blood cell that are built in the same way as integrated circuits.

Materials are deposited in a three dimensional stack on a silicon base and whittled and shaped using photolihography in which ultraviolet light is used for etching. An acid bath at the end washes away unwanted pieces leaving tiny hinges, rotors, or other mechanical elements of the minute silicon machines.

As futuristic as mite size machines like smart dust may sound, several commercial applications of MEMS have already made the leap from the laboratory to the prototype stage and into production. Many more are expected in the next decade.

Analog Devices for example, make dot size motion sensors that are deployed in airbags said Jim Doscher marketing manager of the company's micromachine product division in Cambridge Mass.

The sensors measure deceleration and signal a microchip which decides if the signal is a bad parking job or a crash, Doscher said.

Because MEMS take advantage of the photolithographic techniques used in integrated circuit technology they ae fairly inexpensive..