Researchers create power-generating, gel electret-based device for wearable sensors

A team of researchers from NIMS (National Institute for Materials Science), Hokkaido University and Meiji Pharmaceutical University has developed a gel electret capable of stably retaining a large electrostatic charge. The team then combined this gel with highly flexible electrodes to create a sensor capable of perceiving low-frequency vibrations (e.g., vibrations generated by human motion) and converting them into output voltage signals. This device may potentially be used as a wearable health care sensor.

Interest in the development of soft, lightweight, power-generating materials has been growing in recent years for use in soft electronics designed for various purposes, such as health care and robotics. Electret materials capable of stably retaining electrostatic charge may be used to develop vibration-powered devices without external power sources.

NIMS has been leading efforts to develop a low-volatility, room-temperature alkyl–π liquid composed of a π-conjugated dye moiety and flexible yet branched alkyl chains (a type of hydrocarbon compound). The alkyl–π liquids exhibit excellent charge retention properties, can be applied to other materials (e.g., through painting and impregnation) and are easily formable.

However, when these liquids have been combined with electrodes to create flexible devices, they have proven difficult to immobilize and seal, resulting in leakage issues. Moreover, the electrostatic charge retention capacities of alkyl–π liquids needed to be increased in order to improve their power generation capabilities.