A Locally Amplified Strain Sensor Based on a Piezoelectric Polymer and Organic Field-Effect Transistors

Piezoelectric sensors are useful for a range of applications, but passive arrays suffer from crosstalk and signal attenuation, which have complicated the development of array-based polyvinylidene difluoride (PVDF) sensors. We have used organic field-effect transistors, which are compatible with the low Curie temperature of a flexible piezoelectric polymer, i.e., PVDF, to monolithically fabricate transimpedance amplifiers directly on the sensor surface and convert the piezoelectric charge signal into a current signal, which can be detected even in the presence of parasitic capacitance. The device couples the voltage generated by the PVDF film under strain into the gate of organic thin-film transistors using an arrangement that allows the full piezoelectric voltage to couple to the channel while also increasing charge-retention time. A bipolar detector is created using ultraviolet-ozone treatment to shift the threshold voltage and increase the current of the transistor under both compressive and tensile strain. An array of devices that maps the strain field on a PVDF film surface is demonstrated.