Detailed analysis of flow-induced thermal mechanisms in sub-micron MEMS-based VOC biosensors: A design solution for the nanometer scale

While Micro-Nanoelectromechanical (M/NEMS) resonators have been proposed to operate as gas sensors in the biomedical domain for volatile organic compound (VOC) detection, the impact of fluid flow disturbances on their oscillation frequency is a major concern. The gas stream convectively cools down the vibrating beam and induces thermal stress with a consequent undesired impact on its frequency response. This paper investigates and experimentally demonstrates how a 4-anchored plate resonator specifically incorporating folded beam topology largely mitigates such effects compared to common straight beam thanks to allowing for a differential strain. Folded beams provide a thermal gas-induced stress shift from compressive to tensile reducing the temperature coefficient of frequency (TCF) and, consequently, reduces significantly the fluid flow impact. Experimental evidence supports this local phenomenon to be mostly present on sub-micron beams and predicts it to be accentuated in nanoscale beam geometries.