Electromechanical response of poly(vinylidenefluoride) thin films under acoustic stimuli

Understanding and controlling the vibration of piezoelectric components induced by oscillating external stimuli is essential to develop smart sensing and energy harvesting devices that convert mechanical energy into electricity. Piezoelectric polymers based on poly(vinylidenefluoride) (PVDF) thin films are amongst the most widely studied materials for flexible sensors and harvesters. Despite the large amount of research on these materials, their electromechanical response under acoustic sound stimuli has not yet been studied in detail. In this work, a thorough investigation on the mechanical vibrations and electrical response of PVDF circular plates of different diameters in response to multiple sound wave frequencies (100 Hz-10 kHz) has been carried out to gain further understanding of the resonance behavior and acousto-electric conversion mechanisms of vibrating PVDF thin films. The work is based on experimental data generated using an integrated piezo-acoustic laser vibrometry system and on a theoretical framework based on the continuum theory of thin plates. The developed model enables the prediction of the resonance frequencies in dependence of the plates' diameter, and suggests that the electrical voltage generated during vibrations is not solely originating from the piezoelectric properties of the films, but might be affected by additional factors, including the triboelectric effect. The results of this study are expected to have a strong impact on the investigation of piezoelectric vibrating plates and on the development of different types of transducers and energy harvesting devices.