Polymer/Ceramic MEMS: A Nanomechanical Sensor Platform With Low Temperature High Gauge Factor ITO for Electromechanical Transduction

Abstract

MEMS biochemical sensors based on nanomechanical cantilevers (NMC) translate bio/chemical interactions into nanomechanical motion that can be detected by various transduction techniques. Polymer Nanomechanical Sensors have proven to be better candidates than the conventional silicon MEMS sensors owing to better sensor performance, ease of fabrication and cost effectiveness. In this paper, the development of novel polymer nanomechanical cantilever sensor platform with a high gauge factor Indium tin oxide (ITO) as piezoresistor for electrical transduction has been discussed. With simple and cost-effective polymer MEMS process integration, low temperature deposited ITO has been incorporated for efficient electromechanical transduction of SU-8 microcantilever devices. The fabricated SU-8/ITO microcantilevers were experimentally characterized for extracting the mechanical, electrical, and electromechanical properties. These SU-8/ITO devices exhibited strong negative piezoresistive behavior with the experimentally extracted gauge factor of ITO as -779. These devices show displacement sensitivity of 37 ppm/nm, which is nearly 30 times that of reported values of SU-8 cantilevers with nanocomposites as strain sensitive layer. The surface stress sensitivity is found to be 49.8 ppm [mN/m] <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . One of the potential applications of this polymer MEMS cantilever for room temperature detection of hydrogen gas has also been demonstrated.