Electro-thermally driven microgrippers for micro-electro-mechanical systems applications

Abstract

This paper presents design, fabrication, and performance testing of an innovative, laser machined structure to act as a microgripper. The proposed design constitutes of a pair of identical, cascaded actuation structures oriented in a face-to-face direction, to act as microtweezers. Each microactuator consists of five actuation units joined together horizontally in a consecutive order to build the cascaded structure. The actuation unit incorporates an internal constrainer and two semi-circular-shaped actuation beams. The actuation principle is based on the electro-thermal effect. On application of electrical potential at the backends, the conductive, geometrically complex structure of the microgripper produces non-uniform resistive heating and uneven thermal expansion generating tweezing displacements and force through a cumulative effect of all the individual actuation units within the cascaded microactuators. High-precision laser micromachining process was employed in the fabrication of the copper and nickel-based prototype microgrippers with overall dimension of 1.4 mm(L)×2.8 mm(W) and with relative accuracy within 1%. The geometrical parameters of the prototypes were evaluated in terms of accuracy and precision to demonstrate the fabrication capabilities. Challenges involved and the solutions to develop functional microparts with high aspect ratio (dimensional) with respect to the local elements and overall dimensions were described. The performance of the two microgripper prototypes was analyzed and compared. These microgrippers are useful in micromanipulating and microhandling operations for micro-electro-mechanical systems, biological, medical, chemical, and electro-opto-mechanical engineering applications.