Precision Bonding Makes Tiny High Performance Actuators Possible

Using a new precision bonding process they developed, Penn State researchers have designed and fabricated tiny new piezoelectric microactuators – the largest only a hair’s breadth wide -- based on coupling commercially available materials with existing micromachining technology.

Possible applications of the new Penn State piezoelectric microactuator.

The new actuators promise to be low cost and capable of providing controlled force, high resolution and large displacements appropriate for applications in RF switches for cell phones, for example, or optical switches for wide screen TVs. Other potential applications include microfluidic pumps and valves, micromanipulators for nanoscale handling and atomic force microscope drives.

The new actuators are made from flat strips of bulk PZT, a commercially available piezoelectric material that shrinks slightly when a voltage is applied to it, and a precision micromachined silicon beam. Bonding the silicon beam to the PZT amplifies and converts the PZT shape change into a convex deflection when the silicon beam buckles as the PZT shrinks.

In operation in the actuator, the measured deflection of the silicon beam shows a gain factor of 20 with respect to the PZT dimensional change.

For the bonding process in fabricating the new actuators, the Penn State researchers use photolithography and low temperature solders to produce the distinctive bridge shape they need.

Using their new approach, the researchers have fabricated actuators with dimensions ranging from 350 to 600 microns in length, 50 to 100 microns (about the width of a human hair) in width, and 5 to 6 microns in thickness.

In tests, the actuators showed good repeatability with a large amplitude stroke of about 8 microns when actuated using –100 V to 100 V. The bandwidth of the actuator was measured at 265 KHz.

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