Temperature Induced Inaccuracy in Composite Piezoresistive Micro/Nano Cantilever Chemical/Biological Sensors

Over the years, piezoresistive micro/nano cantilevers have been explored as sensing platforms for realizing chemical/biological sensors. Even though, literature encompasses various design examples of such sensors, seldom a major limitation-joule heating induced thermal drift in sensor output is considered in the modeling and design stages. In this paper, we model and design a piezoresistive micro/nano cantilever surface stress sensor considering thermal drift component and estimate the temperature induced inaccuracy in the sensor output. The composite sensor design is performed at both material and geometric levels considering the interdependence between mechanical, thermal and electrical design variables. Results depict that the magnitude of thermal drift in sensor output is higher than the desired signal. Thus, thermal drift has detrimental impact on sensor measurement reliability. Simulation results show that the major component of thermal drift i.e. TCE induced cantilever defection increases at higher immobilization layer thickness and de-bias voltage. Therefore, to obtain higher sensitivity ratio (electrical sensitivity to thermal sensitivity), lower immobilization layer thickness along with reduced bias voltage should be used. The present work has wide implications since it provides an in-sight into the modeling and design of piezoresistive micro/nano cantilevers with thermal drift phenomenon demonstrating the need for thermal drift aware design of such sensors.