Maximizing microelectromechanical sensor and actuator sensitivity by optimizing geometry

Microelectromechanical systems (MEMS) typically consist of sensor and/or actuator units. In many cases these units are made of beams (modeled as springs) and plates that are subject to external pressure fields, such as electric, magnetic, acoustic or hydrodynamic. Frequently, it is possible to find MEMS devices that can be divided into springs, which control the movement of the device, and an active region, where the sensing or actuating takes place. The overall dimension of a device is often constrained to a small area. In this case it is necessary to find the optimal division between the springs and the active region, which occupy this area, in order to maximize the sensitivity of the device. This paper discusses the relations between the sensitivity of area-constrained MEMS devices and their geometry. The analysis is presented for devices in five different measuring modes, capacitance, tunneling, MOS, piezoresistive and piezoelectric, for a fixed-fixed configuration.