Fabrication and sensing behavior of ultrasensitive piezoelectric microcantilever-based precision mass sensor

We have designed and fabricated a very small microcantilever mass sensor based on a piezo-electric actuation and sensing mechanism for ultrasensitive femtogram detection. We have used the resonant-frequency change of the microcantilever upon a mass increase in the microcantilever surface. The microcantilever was fabricated by using micro-electro-mechanical-system (MEMS) processing. The microcantilever employs a sol-gel-derived Pb(Zr _0.52,Ti_0.48)O₃ (PZT) film capacitor fabricated on a low-stress SiN_x elastic layer for piezoelectric actuation. A mass sensitivity of 3 fg/Hz was achieved with a high mechanical quality factor of 680. The corresponding gravimetric sensitivity factor was 450 cm ²/g, which is significantly larger than that of a quartz-crystal microbalance. This electrically-driven ultrasensitive mass sensor enables application for a precision mass sensor to detect biomarker or virus molecules in a femtogram regime.