Monocharged Electret Generator for Wearable Energy Harvesting Applications

Polytetrafluoroethylene (PTFE)-based electret materials have emerged as one of the most widely used materials in underwater transducer, microphone, and transistor applications. In this paper, it is shown for the first time that a monocharged (single type, electron) PTFE electret material can be used in energy harvesting and self-powered device applications, such as wristband and shoe insole devices. At first, a theory based on the electrostatic effect is derived for the first time for monocharged electret generator (MCEG). For a hand-shaking movement, the MCEG-based wristband device can generate an output voltage and current of 14 V and 0.65 mu A, respectively. Furthermore, it is found that the MCEG-based shoe insole device can generate a maximum output voltage of 178 V and a current of 2.85 mu A during walking. The maximum harvested power obtained is approximate to 35.63 mu W in shoe insole-based devices under a resistor load. Additionally, the power generated from the shoe insole device can light up 55 light-emitting diodes with a single step of walking. Because of the relatively large output power density, ease of fabrication, and chemical stability, this device shows great promise for wearable self-powered device applications.