A combined sensor and a switch based on a chemiresistive material coupled with a resonant microbeam

Abstract

Despite the remarkable advancements to develop low-cost low-energy individual chemiresistive sensors, the complete sensor-actuator systems remain complex due to the implementation of energy-hungry components, such as transmitters, microcontrollers, and analog-to-digital and digital-to-analog converters. In an effort to alleviate this problem, we introduce a simple sensor-actuator platform by electrically coupling a chemiresistive material with a clamped-clamped microbeam and utilizing the nonlinear instabilities of buckling and pull-in. As a case study, we demonstrate the concept using the chemiresistive material Ti₃C₂T_x MXene for humidity sensing and actuation. The device can trigger actions when exceeding a pre-determined relative humidity (RH) threshold. It can also function as a sensor with a quasi-digital resonance frequency output in the sensing mode. Analytical results based on the Galerkin approach are obtained and compared to the experimental data. The results indicate that as RH levels increase, the coupled system of the chemiresistive material with the resonator has more sensitivity compared to the individual chemiresistive sensor. Simulation results are shown to demonstrate the capability of tuning and adjusting the switching thresholds to meet various application needs.