Piezoelectric rubber films for human physiological monitoring and energy harvesting

We have successfully demonstrated the fabrication of piezoelectric rubber films and their applications in heartbeat sensing and human energy harvesting. To realize the desired stretchability and electromechanical sensitivity, cellular PDMS structures with micrometer-sized voids are internally implanted with bipolar charges, which are secured by PTFE surface coating. The resulting composite structures show an elastic modulus about 300 kPa and a piezoelectric coefficient d₃₃ higher than 1000 pC/N. With a pressure sensitivity of 10 mV/Pa, the sensing of heartbeat is demonstrated. Furthermore, multiple piezoelectric films are stacked to form an energy harvester that can charge solid-state energy storages. With a 10-kilogram load over a 10-cm² projected area, a 4-layer stacked structure can deliver a charge of 0.4 μC per cycle. As such, the piezoelectric rubber films can function as both sensing and powering elements, and potentially realize the integration of human physiological monitoring and energy harvesting.