An optically transparent gripper for micro-assembly

This paper describes the development of a novel optically transparent electrostatic microgripper for assembly of micro-electromechanical systems (MEMS). The principle of operation, design and tests of the new device are described. Fabrication sequence and the materials used are also provided. The resulting gripping force is measured as a function of the applied voltage and compared with a parallel pate capacitor model. The frictional (in-plane) force was also determined for two common materials, silicon and nickel. As expected, a small amount of trapped interfacial charge was observed and characterized via scanning potential microscopy (SPM). The present work provides experimental data on the magnitude of the residual charge, the corresponding force, as well as charge decay data. Although undesirable, in the assembly of high-aspect-ratio interconnects, the part release can be achieved via path planning, since the parts are inserted into micro-machined slots. A simple demonstration assembly cell with image- and laser-based position-sensing modalities has also been described.