A Novel Vanadium Dioxide-Based Dual-Heater Microfluidic Thermal Flow Sensor With Record High Sensitivity

High-sensitivity flow measurement technology is a prerequisite for precise dynamic control of microfluidics. Despite the advances in structure optimization, a more efficient approach to improve device sensitivity can be realized by leveraging materials with a higher temperature coefficient of resistance (TCR). This work presents the design and simulation of a vanadium dioxide (VO2)-based microfluidic thermal flow sensor with record high sensitivity. Owing to the phase change property, VO2 demonstrates the maximum TCR of -0.703 and -0.63 K-1 in the major heating and cooling curves, respectively, which is more than two orders of magnitude higher than commonly used thermal-sensitive materials. To fully utilize the high thermal sensitivity of VO2, a dual-heater configuration with enhanced thermal differential effect is proposed, and its sensing performance is evaluated in the flow range below 10 mu L.min(-1). By individually operating the VO2 thermal sensors at critical transition temperatures in the major hysteresis loop, the sensitivity can reach as high as 2.79 V/mu L.min(-1), which is about 187.88 times and 277.89 times higher than the VO2-based anemometer and the Pt-based dual-heater calorimetric (DHC) sensor, respectively. The research in the present work may enable a breakthrough in the improvement of high-performance microfluidic thermal flow sensors in the ultralow flow region using nonstandard metamaterials.