Validation and Characterization of an Acoustic Sensor Based on PVDF Micropillars and Patterned Electrodes

This paper addresses the fabrication, validation, and characterization of a millimeter-size acoustic sensor consisting of Polyvinylidene Fluoride (PVDF) micropillars and patterned electrodes. The sensor takes advantage of two key design principles: stress amplification through the area ratio between the overall surface exposed to acoustic waves and the area of the individual micropillars, and patterned electrodes which reduce the capacitance of the sensor by excluding the capacitance of the air between micropillars. In combination, these design principles enable a sensor capable of achieving 100× the sensitivity of flat PVDF film. A sensitivity analysis is presented and sensor fabrication details are described. An experimental setup was developed to characterize the sensor against a reference microphone. A signal conditioning circuit including a preamplifier circuit and a notch filter was designed and constructed. Sensitivity calibration tests show that a micropillar array with a gap ratio of 5.82 exhibits a stress constant g₃₃ = −19.93 V/m/Pa, which is 60.39 times greater than the stress constant of commercial PVDF film. Experimental results also show that the sensitivity of the sensor is in close agreement with theory, thus confirming the performance advantages of the micropillar sensor.