Composite rubber electret with piezoelectric 31 and 33 modes for elastically electromechanical sensors

This study has demonstrated the design and fabrication of wearable piezoelectric PDMS rubber microstructures with d₃₁ and d₃₃ modes. This PDMS microstructure shows a strong piezoelectricity with effective piezoelectric coefficient (d₃₁) and (d₃₃) of approximately 235 and 3350 pC/N, the lower effectively elastic modulus (E) and spring constant (k) are approximate 300 kPa and 250 N/m, respectively. PDMS microstructures have micrometer-sized voids inside and open channels, which can connect to ambient atmospheres. Internal patterns inside rubber electrets can be designed and adjusted its piezoelectricity, by means of utilizing multi-layer casting, stacking, surface coated with PTFE films, elastic gold films as flexible electrodes, and micro plasma discharge processes applied with a triangular waveform and electric field of 35 MV/m for 15 minutes at 100 °C to produce the functions as electrets. In conclusion, the piezoelectricity of PDMS microstructures could be tailored by adjusting the dimensions of the cellular voids, and potentially serve as wearable, stretchable MEMS devices with high sensitivities.