Mass Sensors Based on Capacitive and Piezoelectric Micromachined Ultrasonic Transducers—CMUT and PMUT

Microelectromechanical system (MEMS)-based mass sensors are proposed as potential candidates for highly sensitive chemical and gas detection applications owing to their miniaturized structure, low power consumption, and ease of integration with readout circuits. This paper presents a new approach in developing micromachined mass sensors based on capacitive and piezoelectric transducer configurations for use in low concentration level gas detection in a complex environment. These micromachined sensors operate based on a shift in their center resonant frequencies. This shift is caused by a change in the sensor’s effective mass when exposed to the target gas molecules, which is then correlated to the gas concentration level. In this work, capacitive and piezoelectric-based micromachined sensors are investigated and their principle of operation, device structures and configurations, critical design parameters and their candidate fabrication techniques are discussed in detail.

A Micromachined Contactless Suspension With Zero Spring Constant

In this paper, a micromachined contactless suspension with a zero spring constant that provides possibility to significantly increasing sensitivity of micromachined sensors is studied. Minimization of the spring constant of the contactless suspension is achieved by combining inductive and electric contactless suspensions. In particular, the conditions required to eliminate the spring constant of the suspension and achieve stable levitation of the disk shaped proof mass are obtained based on the analysis of developed mathematical model of the suspension. It is shown that such a suspension can be developed in principle.