US Patent 7140261 Acoustic wave flow sensor

An acoustic wave flow sensor is disclosed, which includes a sensor substrate and an acoustic wave diaphragm etched upon the sensor substrate, wherein mechanical stress or strain is concentrated in the acoustic wave diaphragm. One or more interdigital transducers can be configured upon the acoustic wave diaphragm, wherein the sensor substrate, the acoustic wave diaphragm and the interdigital transducer(s) form an acoustic wave flow sensor, such that when the interdigital transducer and the acoustic wave diaphragm are exposed to a fluid in flow, the fluid in flow causes the acoustic wave diaphragm to experience a change in the mechanical stress or strain resulting in a detectable frequency and/or phase change in order to provide an indication of fluid flow.