This article first appeared in Personal Computer World magazine, February 2000.

To most of us, dust is a nuisance. It clogs up our PCs and spoils our houses. But there's a growing community of researchers who believe dust could be the Next Big Thing. The dust they have in mind, however, will be "smart", and each tiny particle of it will be a fully-functioning computer.

Kris Pister, of the University of California at Berkeley, is leading a team whose goal is to create devices no bigger than one-millimetre cubes. Each device, or "mote", will contain sensors, an on-board computer and power supply, and an optical communication system, enabling it to talk to other motes and conventional computers.

The key to Pister's ambition is a technology called MEMS (Micro Electro-Mechanical Systems), which permits microscopic mechanical structures to be created using the same photolithographic techniques used to make silicon chips. Pister's current prototype device is a 5-millimetre cube, into which is packed an amazing collection of components: a steerable laser diode transmitter, an optical receiver and passive optical transmitter, a CPU, and a battery with a solar-cell charger. In two years' time it should be possible to shrink the mote to sub-millimetre size.

The idea is that each mote is entirely self-contained, and includes an environment sensor, whose data can be broadcast to other motes or an external computer. Pister's team has chosen optical communication rather than radio because optical systems require less power. They've already demonstrated the effectiveness of the technique by monitoring a weather station broadcasting its data using a modified laser pointer -- over an impressive 21km distance.

As for sensors, a range of prototype motes have already been built which can monitor temperature, humidity, pressure, illumination, spatial orientation and magnetic fields. Currently, there's enough power on board to keep a mote in continuous operation for about a week, but this will get longer as techniques are developed for dynamically shutting down parts of the circuitry when they're not in use.

The potential of having hundreds or even thousands of these motes monitoring an environment is enormous. Suggested applications include truly wireless and unencumbered 3D interaction: with orientation-sensitive motes dusted over your fingers, your gestures could be precisely relayed to a computer which interprets them as commands for sculpting in virtual clay, for example, or playing musical instruments. Foodstuffs could be dusted with motes sensitive to moisture or acidity, which report when the food is past its "best by" date. Then there's the whole area of interfaces for the disabled: to precisely and unobtrusively monitor tiny muscular movements, or to translate sign language gestures. Another possibility is to create "smart offices", which automatically adjust their temperature and humidity in response to the requests of smart dust sprinkled on our clothing, or even our skin.

But Pister's funding comes from DARPA, the US agency for military research, so there's a strong bias towards the possible military applications of smart dust. On his Web page, he's understandably coy about the details of such applications, mentioning only ideas like battlefield surveillance and Scud missile hunting.

Some technology observers have suggested more insidious uses for smart dust, especially in the realms of surveillance. Imagine a cloud of dust released into a room. Perhaps one or two of the dust particles will be smart, capable of monitoring your conversation, or even videoing you, and quietly transmitting the data to an eavesdropper who may be many miles away.

Pister is philosophical about such suggested applications. "Every technology has a dark side," he says, "so deal with it". But with an almost invisible technology like smart dust, the real problem is that you can never be sure what it is you're dealing with.

Toby Howard teaches at the University of Manchester.