Distributed MEMS Mass-Sensor Based on Piezoelectric Resonant Micro-Cantilevers

Abstract

We have realized a distributed mass-sensor using micro-cantilevers. The micro-cantilevers were actuated using piezoelectric ZnO thin films. The micro-cantilevers layer stack consists of Si/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Pt/ZnO/Pt layers for self-actuation of devices. The mass sensing performance was evaluated by laser Doppler vibrometer. Experimentally, micro-cantilever length was varied in the 100-300-μm range, and it is established that masssensitivity increases with reducing length of cantilevers. New relationship has been derived between mass sensitivity (S) and cantilever length (l), which follows the modified power law as S ∝ 1/l <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.8</sup> . Remarkable mass-sensitivity (S = 0.3138 Hz/pg) was obtained for a smallest size cantilever, which has dimensions 100 × 50 × 8.3μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . Optimal mass sensor shows high-quality factor (Q ~ 234) at room temperature and one atmospheric pressure. Such ZnO-based mass sensors are biocompatible, safe, and promising candidate for chemical and bio-sensing applications.