Laterally Movable Gate Field Effect Transistors for Microsensors and Microactuators

Abstract: A field effect transistor is disclosed whose output is modulated by a control gate that is movable in a direction parallel to the transistor substrate surface. The device is capable of lateral motion with large amplitude (tens of micrometers) with appropriate selection of gate materials and design. The transistors may be used in microsensors or microactuators. When used as a microsensor, the gate may be driven parallel to the substrate by the force to be measured (such as an inertial force). When used as a microactuator, the gate may be driven by an actuating drive such as an electrostatic, magnetic, or thermal actuation. The device measuires or controls the displacement of a mechanical structure parallel to the transistor substarte. The change in the output current of the transistor is a linear function of the in-plane displacement of the gate, allowing direct mechanical displacement-to-current conversion. This direct, linear conversion provides improved sensitivity, improved signal-to-noise ratio, and improved signal conditioning and signal processing. It allows precise measurement, actuation, and control of lateral displacement.