“There was nothing in the [optics] literature to predict that this would happen,” says Sandia National Laboratories researcher Dustin Carr of his group’s device, which reflects a bright light from a very small moving object.
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Like shadow pictures projected onto a wall by shining light through the fingers of one hand moving over the fingers of the other, the relatively simple measuring device depends upon a formerly unrecognized property of optics: light diffracted from very small gratings that move very small lateral distances undergoes a relatively big, and thus easily measurable, change in reflection.
A motion of 10 nanometers can be seen by the naked eye, says Carr. A nanometer is one-thousandth of a micron, which is one millionth of a meter. As for the device, size matters and small is crucial. “In standard MEMS [microelectromechanical] applications, though the devices are small, very few things that sell are dominated by a search for further miniaturization.
There’s not a motivation in MEMS to make things still smaller as a matter of cost. Economics of scale for integrated circuits just don’t apply to MEMS. But our device couldn’t exist unless you made it this small,” he says. Features are in the 100-200 nanometer range, with 300 nm between top and bottom combs and 600 to 900 nm between comb teeth.
