A Thermal-Piezoresistive Self-Sustained Resonant Mass Sensor with High-Q (>95k) in Air

Abstract

This paper demonstrates, for the first time, a high sensitivity mass sensor based on thermal-actuation piezoresistive-detection coupled resonators with a selfsustained oscillation. In-plane-vibration resonators are actuated by thermal expansion and contraction of the nanobeams, while the vibration displacements are detected by changes in resistance. Due to the combination of the negative piezoresistive coefficient of the phosphorusdoped structural silicon layer and the thermal expansion/contraction effect, a constant direct current (DC) through the nanobeam produces a periodic resistance variation in the beam at the fundamental modal frequency as the resonator, thus a self-sustained oscillation is generated. An ultra-high quality factor of ~95k in air is obtained. Linear response with respect to mass perturbations for both amplitude ratio (of the two coupled resonators) and frequency shift readouts are observed from the proposed self-oscillating, mode-localized mass sensor. The measured sensitivity of the amplitude ratio (~162 ppm/pg) is 100 times higher than that of a shift in the normalized resonant frequency.

A Fast-Startup Self-Sustained Thermal-Piezoresistive Oscillaror with >106 Effective Quality Factor In The Air

“…3 illustrates the principle of the thermal-electric-mechanical interaction. A more detailed description can also be found in [7]. The nanobeam plays the role of both actuating the resonator and detecting the movement as well.…”

“…The Q-factor is a measure of the energy dissipation in a specific working mode, and is a critical parameter to improve the signal to noise ratio (SNR) of force sensors, phase noise of oscillators and noise rejection of filters [6]. In previous work, we have already introduced a mass sensor with two coupled resonators using the thermal-piezoresistive principle with a Q-factor of ~95k in atmospheric environment [7]. However, associated with a high effective Q-factor, the startup time of the oscillator usually increases as well, limiting the applications that require periodic oscillator startup [8].…”

Silicon Carbide-on-Insulator Thermal-Piezoresistive Resonator for Harsh Environment Application

“…Since the first miniature Si piezoresistive heat engine was reported in 2011 [1], a variety of self-sustained thermal-piezoresistive resonators or oscillators have been developed for mass sensing [2,3], Lorentz force measurement [4], gas detection [5], and signal amplification [6]. It was demonstrated that the thermalpiezoresistive effect is strong enough to initiate and maintain the mechanical oscillation of the resonator driven by direct current (DC), without the demand for any external alternating current (AC) source and amplifying circuitry.…”