Enhancement of real-time resonance tracking in electrothermally actuated cantilever sensor with optimized phase characteristic

Non-ideal phase responses on electro-thermally actuated piezoresistive cantilever sensors have led the phase-locked loop (PLL) systems into difficulties for real-time sensing applications. These outcomes are caused by thermal-parasitic coupling from the actuating part to the sensing part. Minimizing or eliminating parasitic effects is necessary to obtain an optimized phase response. To realize this, we adjusted the voltage supply of the sensing part, which is in form of a full Wheatstone bridge (WB). By increasing the WB supply voltage (V WB), the phase response can be enhanced. Alternatively, a reference signal that differentially eliminates the parasitic parameter from the sensor output was employed. To investigate the resulting optimized phase response under real-time measurement conditions, two different microcantilevers were connected to an MFLI lock-in amplifier + PLL system (Zurich Instruments). Measurement results exhibited a good sensor performance under varying humidity and temperature conditions.