Cheaper, better motion detectors on the way

MIT researchers have created miniature motion sensors for use in cellphones and games controllers that don’t involve high-tech manufacturing facilities and come in at a tenth of the price.

At MIT’s Center for Bits and Atoms (CBA), they’ve built a motion sensor that consists of a tiny metal bead suspended in what the center’s director, Neil Gershenfeld, describes as “a hole drilled in a circuit board.”

A fluctuating electric field holds the bead up in a tight orbit, and disturbances of the orbit indicate the sensor’s direction of motion.

The device can do the work of at least six different micromechanical sensors, says Gershenfeld. It can measure linear motion in three dimensions, which would usually require three accelerometers.

But it can also gauge its orientation — whether it’s tipped sideways or forward, or been rotated — which would usually require an additional three gyroscopes.

This means motion detection in handheld devices could become much more precise. The Wii game controller, for instance, wouldn’t need an infrared emitter mounted to the television, and the Apple iPhone would change its screen orientation more reliably.

The three-axis accelerometer is the most expensive component of the Wii remote, and the team reckons a six-dimensional microdynamical sensor could be manufactured for about a tenth as much.

“If they can get all six degrees out of it, it would be huge,” says Michael Judy, a researcher at Analog Devices, the company that built the Wii’s accelerometers. “That’s the holy grail right now in the human interface to electronics.”