Enhancing the Sensitivity of a Thermal Microflow Sensor: A Comprehensive Modeling and Simulation Study

The advancement of microfluidic technology has introduced new requirements for the sensitivity of microflow sensors. To address this, this paper presents a novel high-sensitivity thermal microflow sensor incorporating a heat-insulating cavity structure. The sensor utilizes porous silicon as the substrate and employs vanadium dioxide as the thermistor element. This study employed COMSOL Multiphysics finite element software 5.6 to investigate the impact of materials and structural factors on the sensor's sensitivity, as well as considering the dynamic laws governing their influence. Additionally, the effects of thermal expansion and thermal stress on the microstructure of the sensor are thoroughly examined. The research results show that the sensitivity of the sensor was influenced by key factors such as the distance between the heater and the thermistors, the diameter of the flow channel, the power of the heater, and the presence of an insulation cavity. The utilization of B-phase vanadium dioxide, known for its high temperature coefficient of resistance and suitable resistivity, led to a significant reduction in sensor size and a remarkable improvement in sensitivity. The implementation of four thermistors forming a Wheatstone full bridge further enhanced the sensor's sensitivity. The sensor's sensitivity was substantially higher when employing a porous silicon substrate compared with a silicon substrate. Moreover, the integration of a micro-bridge and four micro-beams composed of silicon nitride into the sensor's structure further improved its sensitivity. The proposed design holds promise for enhancing the sensitivity of thermal microflow sensors and offers valuable insights for future advancements in MEMS technology.