New 'nano-positioners' may have atomic-scale...(d inducing an attraction between the opp...)

By comparison, the new monolithic device has a single structure with two perpendicular comb drives.

Clark calls the device monolithic because it contains comb drive components that are not mechanically and electrically separate. Conventional comb drives are structurally "decoupled" to keep opposite charges separated.

"Comb drives represent an advantage over other technologies," Clark said. "In contrast to piezoelectric actuators that typically deflect, or move, a fraction of a micrometer, comb drives can deflect tens to hundreds of micrometers. And unlike conventional comb drives, which only move in one direction, our new device can move in two directions - left to right, forward and backward - an advance that could really open up the door for many applications."

Clark also has invented a way to determine the precise deflection and force of such microdevices while reducing heat-induced vibrations that could interfere with measurements.

Current probe-based biological sensors have a resolution of about 20 nanometers.

"Twenty nanometers is about the size of 200 atoms, so if you are scanning for a particular molecule, it may be hard to find," Clark said. "With our design, the higher atomic-scale resolution should make it easier to find."

Properly using such devices requires engineers to know precisely how much force is being applied to comb drive sensors and how far they are moving. The new design is based on a technology created by Clark called electro micro metrology, which enables engineers to determine the precise displacement and force that's being applied to, or by, a comb drive. The Purdue researcher is able to measure this force by comparing changes in electrical properties such as capacitance
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