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Cheapening the Cost of Motion Sensors

Motion sensors are starting to creep into a whole plethora of applications. They are the linch pins of haptics, of 3D pointers, of stress based sensor networks and locomotive VR interfaces. Yet, there's a problem. Small, discrete motion sensors, tiny enough to be built into larger devices the size say, of a Wii-remote or a 6 ounce HMD, are extremely difficult and expensive to produce.

They require a similar level of precision to the manufacture of silicon chips - and a similar level of expense. If a way could be found to produce them at a substantially cheaper cost, the knock-on effect would go a long ways towards bringing everything from prosthetic limbs to sensor wands much closer to mainstream.

A new approach, pioneered by MIT, looks to offer real hope of that for the first time. Researchers at MIT's Center for Bits and Atoms (have built a motion sensor that consists of a tiny metal bead suspended in what is essentially a microscopic hole drilled in a circuit board. The same boards that comprise the mainstay of most devices in fact.

This bead is held aloft in the middle of the hole by a tiny fluctuating electric field. This allows it to do the work of six normal sensors, as the bead is free to move in all three axis within the space - up, down, left, right, front, back, all with a single sensor. This is an immediate reduction in cost six-fold, and change. The lack of mechanical parts greatly further reducing cost of the sensor, whilst the reduction in sensor number reduces both bulk and weright for a full three axis (six degrees of freedom) sensor.

In this image, you can see the bead suspended in a 100 micrometer wide hole in the circuitboard - no wider than a single wire thread..

"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." Judy says that the application of motion sensing that has sparked the most interest is navigation in environments where GPS information is either unreliable or too imprecise. For instance, local spatial tracking would let hospital workers immediately determine each other's locations, even on different floors of a large building.


Microsensors without microfabrication

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