Development of an electron tunneling force sensor for the use in microassembly

We present the development of an electron tunneling force sensor for use in microassembly and micromanipulation tasks. The force sensor consists of flexible structural members, to which two electrodes are attached, which deflect under the application of grasping forces, and a thermal actuator. A feedback controller is developed to maintain a constant tunneling current across the two electrodes, thereby maintaining constant displacement of the electrodes. Measurement of the voltage applied to the thermal actuator to maintain a constant electrode displacement allows the grasping force to be determined. The design and modeling of the force sensor are addressed. The fabrication of sharp tunnel tips using commercially available MEMS process is investigated. A sharp tunnel tip with width less than 100 nm is achieved using the PolyMUMPs process. The electron tunneling force sensor has extremely high sensitivity, which make it very suitable for micromanipulation tasks.