Simple piezoelectric microbalance based on a vibrating quartz wire

The microbalance is based on the mass dependence of the resonance frequency of a vibrating quartz wire, from which loads are suspended and that is connected to two piezoelectric flexure elements. The set-up can be used in various ambient conditions (temperature, pressure, humidity, gas composition), it is essentially drift free and, moreover, extremely simple, rugged and small. For the prototype described the load-to-sensitivity ratio approaches 106 for a free hanging 3 mg load (minimum detectable mass difference about 10 ng).