MEMS Thermo-Nanomechanical Membrane Flexure (T-NMF) Device for Temperature Sensing

Abstract

A promising choice for mechanical sensing applications is the nanomechanical cantilever sensor (NMC), which converts physical change on the cantilever surface into nanomechanical motion that may be detected by suitable transduction techniques. Structural modification of this device into an optimized membrane-based sensor platform and the integration of highly sensitive transduction materials to the NMC sensors can lead to appreciable enhancement in the performance of the sensor, thereby creating an ultra-sensitive nanomechanical sensor platform. This paper reports the development of a MEMS Thermo-Nanomechanical Membrane Flexure (T-NMF) sensor for meeting the demand for a highly sensitive, miniaturized, realtime temperature sensor, based on the principle of deflection of the bimorph membrane with change in temperature, due to the difference in thermal coefficients of expansion of different layers of materials present on the membrane. Four inverse trapezoidal flexures are used to suspend the circular membrane of the T-NMF sensor. The two layers of the membrane are selected to be silicon and aluminum. A thin film of Indium Tin Oxide (ITO), which has a high gauge factor, is deposited as a piezoresistor on each of the flexures, for electromechanical transduction. The design and simulation of the T-NMF sensor is carried out using COMSOL Multiphysics 6.0 software, after optimizing the beam geometry. This optimized design showed an improved thermal sensitivity of around 2 times higher than that of the conventional cantilever bimorph sensor of comparable dimensions.