A monolithically integrated active matrix microphone incorporating local sensing, switching, and amplification

Array microphones have a variety of applications including directional listening, speaker localization, ultrasonic imaging, and boundary layer turbulence measurement.[1][2] Two approaches are commercially used for these applications; arrays of discrete microphones, and one dimensional arrays of electroded piezoelectric materials directly connected to amplification circuitry.[3] Two dimensional array designs using piezoelectric sensors require local amplification at the sensing site to overcome charge sharing through interconnect and switching parasitics. While hybrid silicon-based designs have been proposed for 2-D active matrix microphone systems, these have been based on bulk or thinned crystalline silicon, which can compromise the acoustic properties of the microphone and have a limit on their ultimate size. We have demonstrated a monolithically integrated two dimensional active matrix microphone fabricated on a flexible polymer piezoelectric sheet which uses thin film organic field effect transistors to both locally amplify the piezoelectric charge signal and switch individual elements, allowing for sensing site localization. The integrated design of the sensor and amplifier eliminates a previously dominant parasitic capacitance, allowing an acoustic bandwidth response, and the flexible, thin film form factor allows maximum versatility in applications. The device is tested using both turbulent air current and far field acoustic excitation in this work.