Micro/nano-electromechanical system (M/NEMS) resonators have been widely applied in the fields of sensing, communication, and biomedical diagnosis. Frequency-modulated resonant sensors that transduce a physical or chemical quantity to be measured into a shift in resonant frequency are extremely attractive. Resonant mass sensors have been employed for biochemical applications for weighing single molecules, proteins, and nanoparticles, and even monitoring the growth of living cells. Great challenges for MEMS resonant mass sensors include (i) Improving the sensors’ quality factor (Q-factor) at ambient atmospheric pressure and realizing a real-time monitoring system with high sensitivity are the two great challenges that resonant sensors face. The project “MOSTAPDE” aims to develop a thermal-piezoresistive resonant mass sensor with a mode localization phenomenon to address the above-mentioned challenges.
The following milestones are approached during the progress:
(1) Developed the dicing-free fabrication process for thermal-piezoresistive resonators, demonstrating the fundamental basis and the feasibility of this project.
(2) Simulated the mechanical characteristics of the thermal-piezoresistive resonators, and observed physical self-oscillation when being excited by the current.
(3) Fabricated single degree-of-freedom thermal-piezoresistive resonators as well as coupled thermal-piezoresistive resonators, and constructed the measurement setup.
(4) Characterized the fabricated devices and obtained some exploitable results which have not been reported yet, and published several papers on this topic.
The objectives listed in the DoA include:
(1) Establish a theoretically analytical framework and a finite element model (FEM) of the WCRs, with multi-physics simulations coupling the mechanical, thermal and electrical fields using COMSOL Multiphysics and CoventorWare, as design tools for the sensor and circuit developments.
(2) Develop the mass sensor as well as its fabrication process, to integrate on a silicon wafer substrate weakly coupled resonators, thermal actuation elements and piezoresistive detection gauges.
(3) Design a closed-loop control circuit for the proposed mass sensor to realize real-time monitoring at ambient pressure with high resolution and short response time.
