Preparation and optimization of PVDF thin films for miniaturized sensor and actuator applications

Abstract This paper demonstrates the key process optimizations that need to be carried out in order to leverage the piezoelectric property of polyvinylidene diflouride (PVDF) thin films for miniaturized sensor and actuator applications. The emphasis of the paper is two fold. Firstly, innate material and piezoelectric properties of PVDF thin films were thoroughly investigated and the processing conditions for achieving minimally porous, smooth thin film exhibiting superior piezoelectric response was experimentally figured out. Along with that, as a proof of concept, a working prototype of piezoelectric micromachined ultrasonic transducer (PMUT) was fabricated and tested using optimized PVDF thin films. The key bottleneck of adhesion of PVDF with underlying metal layers is addressed by using adhesion promoter (3-aminopropyl)triethoxysilane. This small, yet significant modification enabled the fabrication of PMUT device using PVDF as membrane material. The fabricated device has exhibited a electromechanical coupling coefficient value of 15.66% and a resonance frequency of 129.5 kHz.