27 August 1999

Date: Thu, 26 Aug 1999 16:15:48 -0700
To: die@pig.die.com
From: Richard Crisp <crisp@rambus.com>
Subject: Dust can really "bug" you

http://www.newscientist.com/ns/19990828/newsstory2.html

New Scientist, 28 August 1999

## Dust bugs

Duncan Graham-Rowe

CLEANLINESS FREAKS have a new rationale for their pathological hatred of dust--it could soon be spying on them.

Packed full of sensors, lasers and communications transceivers, particles of "smart dust" are being designed to communicate with one another. They could be used for a range of applications from weather monitoring to spying.

The tiny "motes" are being developed at the University of California, Berkeley, as part of a programme to produce the smallest possible devices that have a viable way of communicating with each other.

Each mote is made up of a number of microelectromechanical systems, or MEMS, wired up to form a very simple computer. At present each mote is 5 millimetres long, but Kris Pister, one of the developers, says that in future they could be small enough to remain suspended in air, buoyed by the currents, sensing and communicating for hours.

The latest version (see Diagram) not only has a thick-film battery powering it but also a solar cell to recharge it. "This remarkable package has the ability to sense and communicate, and is self-powered," says Randy Katz, a communications engineer on the project. He presented the latest work at last week's Mobicom99 mobile computing meeting in Seattle.

MEMS are made using the same photolithographic techniques as integrated circuits, so once perfected they should be easy to mass-produce. Patterns are etched out of a silicon wafer to create structures such as optical mirrors or tiny engines.

Each mote in a smart-dust system will need to survive on extremely low power, while being able to communicate kilobits of data per second. To this end, says Katz, the team has designed motes that shut down parts of themselves when they are not being used.

The latest challenge has been to devise a system that enables the motes to communicate. Katz and his colleagues decided to use optical transceivers because of their low energy demand compared with radio communications. According to Pister they have already shown that they can monitor the dust 21 kilometres across San Francisco Bay. "There's no way you're going to get that kind of range except with optical devices," he says.

"The base station may actually reside in a hand-held unit, much like a pair of binoculars," says Katz. This would allow for simultaneous viewing of the scene from afar while superimposing any measured data on the image. He adds that this approach could be especially useful for hazardous applications such as detecting chemical weapons or sending the dust into space.

The next task is to build distributed intelligence into the dust to produce "swarm behaviour."

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Richard Crisp
Rambus Inc
2465 Latham St
Mountain View, Ca. 94040
crisp@rambus.com