ELECTROSTATICALLY EXCITED AND CAPACITIVELY DETECTED FLEXURAL PLATE WAVES ON THIN SILICON-NITRIDE MEMBRANES WITH CHEMICAL SENSOR APPLICATIONS

A new method for excitation and detection of flexural plate waves on thin silicon nitride membranes has been developed. The interdigital transducers employ electrostatic and capacitive principles. They operate without a piezoelectric substrate or layer. A micromachined FPW resonator based on the new principles has been developed and tested in practice. Due to the extremely thin membrane, the design allows the development of very sensitive gravimetric chemical and biological sensors working in gases, liquids and gels. A microcontroller signal processing unit has been built for controlling the FPW delay line input and for measuring the output parameters. With this unit, sensor response processing and drift compensation is achieved by means of software.