A self-bended piezoresistive microcantilever flow sensor for low flow rate measurement

This paper presents the fabrication and characterization of a curved-up piezoresistive microcantilever flow sensor. The microcantilever sensor, fabricated with silicon-on-insulator (SOI) wafers, consists of two layers of silicon dioxide and a silicon piezoresistor in-between. The difference in the residual stresses between silicon and silicon dioxide layers curves the microcantilever upwards and the free-end bends out of plane. The curved-up microcantilever transfers fluidic momentum that acts on it to drag force, which bends the curved-up microcantilever and changes the resistance of the piezoresistor. This configuration has the advantage of high sensitivity for low flow rate measurement and allows the microcantilever to be integrated in microchannels to measure steady flow. The flow sensor is calibrated with respect to low flow rates at range of 0–20 cm/s. The sensitivity, repeatability, and zero drift are characterized in detail.