Flexural plate wave sensor and array

A flexural plate wave sensor comprising:

• a substrate having a recess disposed in an upper surface thereof;
• a membrane layer disposed on the upper surface of said substrate;
• a cavity disposed between a portion of said membrane layer and said recess in said substrate;
• a piezoelectric layer disposed on said membrane layer;
• a first transducer disposed on said piezoelectric layer;
• a second transducer disposed on said piezoelectric layer, spaced from said first transducer;
• and
• an absorptive coating disposed on said portion of said membrane layer within said cavity.

A flexural plate wave sensor array comprising:

• a substrate;
• a plurality of flexural plate wave sensors, each sensor including a cavity formed in the substrate, a thin film membrane layer spanning the cavity, a piezoelectric layer disposed on the thin film membrane layer, a transducer disposed on the piezoelectric layer and an absorbtive coating disposed on said thin film membrane layer within said cavity;
• a reference flexural plate wave sensor including a cavity formed in the substrate, a thin film membrane layer spanning the cavity, a piezoelectric layer disposed on the thin film membrane layer and a transducer disposed on the piezoelectric layer;
• and
• a microprocessor electrically connected to each of the plurality of flexural plate wave sensors and said reference flexural plate wave sensor, for monitoring resonant frequency characteristics of the sensors.

A flexural plate wave sensor array comprising:

• a substrate;
• a plurality of flexural plate wave sensors, each sensor including a cavity formed in the substrate, a thin film membrane layer spanning the cavity, a piezoelectric layer disposed on the thin film membrane layer, a transducer disposed on the piezoelectric layer and an absorptive coating disposed on said thin film membrane layer within said cavity;
• a drive amplifier which receives a drive input and outputs an amplified drive output;
• a multiplexer which receives said amplified drive output and a selection signal, for driving one of said plurality of flexural plate wave sensors;
• and
• an output amplifier which senses an output from said one of said plurality of flexural plate sensors and outputs an amplified sensed signal.