Vanadium Dioxide-Based High Sensitivity Dual-Heater Calorimetric Microfluidic Sensor

This paper reports a novel microfluidic thermal flow sensor based on the phase-change material. By operating the VO
2
thermal-resistive sensor in the phase transition region, the temperature coefficient of resistance (TCR) can reach as high as
$-0.43\ \mathrm{K}^{-1}$
, which is several orders higher than conventional thermal sensitive materials. A dual-heater calorimetric sensing configuration is also proposed, allowing individual control of each sensing element operating at the optimal working temperature and further increasing the sensitivity in the flow range of 0 to 0.2
$\mu \mathrm{L}\cdot{\min}^{-1}$
, Results show that the VO
2
-based dual-heater calorimetric flow sensor demonstrates a maximum sensitivity of 1.34
$\mathrm{V}/(\mu \mathrm{L}\cdot{\min}^{-1})$
, which is 80.50 times higher than the anemometric sensor, and 127.35 times higher than the same dual-heater configuration with Pt as the thermal sensitive material. The studies presented in this work may shed light on using thermal flow sensors in the ultra-low flow range.