A micromachined suspended plate viscosity sensor featuring in-plane vibrations and integrated piezoresistive readout

We present a novel resonant miniaturized sensor for the viscosity of liquids. The sensing element is a rectangular plate suspended by four beam springs. This plate vibrates in-plane. Thus, the plate's contribution to the device damping is low, but the plate increases the moving mass of the resonator. This principle aims at improving the quality factor, and gives additional freedom to the device designer. The sensor was fabricated by micromachining, and features Lorentz force actuation and piezoresistive readout. We present a device prototype and show by experiment, that the quality factor of the sensor is an appropriate measure for the viscosity.