Silicon carbide (SiC) micromechanical self-sustained Oscillator operating in liquid

Abstract

This digest paper reports on the first experimental demonstration of self-sustained feedback oscillators referenced to silicon carbide (SiC) beam micromechanical resonators operating in liquid, showing greatly enhanced effective quality factors (Qeff) and good frequency stability. With optical excitation, opto-electrical readout and feedback control, a SiC doubly-clamped beam (dimensions: 100×15×0.5μm) is observed to attain self-sustained oscillation at its fundamental flexural mode of ∼345kHz in water with ∼700-fold Q improvement. For the first time, frequency stability is quantified in such an in-liquid feedback oscillator, with τ ∼10−4 in water for even relatively long averaging time (τ>100s). We also demonstrate the capability of the SiC oscillator for in-liquid microsphere sensing and estimate this oscillator has a mass responsivity of ∼17.2Hz/pg. Such SiC micromechanical self-sustained oscillators, together with the appealing mechanical, optical properties of SiC [1], plus its biocompatibility [2] and chemical stability in solutions, open new possibilities for real-time biosensing and in-situ monitoring of cells and molecules in liquid.