MEMS thermal-piezoresistive resonators, thermal-piezoresistive oscillators, and sensors

Microelectromechanical systems (MEMS) thermal-piezoresistive resonator (TPRs) and thermal-piezoresistive oscillator (TPO) use thermal actuation and realize feedback through the piezoresistive effect. They have the advantages of simple manufacturing, high resolution, and low feedthrough. In particular, the piezoresistive effect can be used to realize thermal pumping to extract energy from a power supply and transmit it to the resonance structure. This can significantly improve the effective quality factor of the resonator and even realize spontaneous high-frequency oscillations, which has attracted significant interest from researchers. The combination of self-sustained oscillation with high quality factors of TPRs can perform various sensing applications and give excellent performance. This article provides a detailed introduction to the working principles of TPRs and thermal pumps and discusses methods to optimize their performance. Then, the manufacturing technologies of TPRs are summarized. Finally, applications of the resonators in sensing mass, magnetic fields, and displacement are reviewed.