On-chip self-sensing function of 4×4 matrix micromachined resonating piezoelectric membranes for mass detection applications [biosensor/chemical sensor applications]

In this paper, we studied the dynamic behavior of micromachined piezoelectric membranes (PMs) as an alternative to QCM biosensors. We use standing waves on our mechanical structures to obtain higher integration density. The 4×4 matrixes of PMs use PZT as a piezoelectric film whose geometries have been drawn by lift-off techniques. Each PM (circular shaped, with a radius equal to 150 μm) can be individually addressed for actuation and/or sensing. Here we show that the same kind of PMs exhibit excellent self-sensing capabilities by using the direct piezoelectric effect of the PZT layer. The open-loop resonant frequencies of several PMs were measured by examining the self-induced charge on the sense electrode using a proximity electronic circuit. We simultaneously performed resonant frequencies measured by means of a dynamic optical interferometer that completely matched the electrical self-sensed resonant spectra. In this case, the PMs were actuated in two different ways, either by using an external transducer or by using the self-actuating (reverse piezoelectric effect) capability of each membrane.