A new energy-generating device based on Gel Electret Tech technology

1. A team of scientists from NIMS, Hokkaido University and Meiji Pharmaceutical University have developed a gel electret capable of stably maintaining a high electrostatic charge. The team then combined this gel with highly flexible electrodes to create a sensor capable of receiving low-frequency vibrations (e.g. vibrations generated by human movement) and converting them into output voltage signals. This device could potentially be used as a portable sensor in healthcare.

2. In recent years, there has been increasing interest in the development of soft, lightweight energy-generating materials for use in soft electronics for various purposes, such as healthcare and robotics. Electret materials capable of stably maintaining an electrostatic charge can be used to develop vibration-driven devices without external power sources. NIMS is leading efforts to develop a low-volatile, room-temperature alkyl-π liquid composed of a π-conjugated dye moiety and flexible but branched alkyl chains (a type of hydrocarbon compound). Alkyl-π liquids have excellent charge retention properties, can be applied to other materials (e.g. by painting and impregnation), and are easily shaped. However, when these liquids were combined with electrodes to create flexible devices, they were found to be difficult to immobilize and seal, resulting in leakage problems. In addition, the electrostatic charge retention capacity of alkyl-π liquids had to be increased to improve their energy-generating capabilities.

3. A research team recently managed to create an alkyl-π gel by adding trace amounts of a low molecular weight gelling agent to an alkyl-π liquid. The elastic modulus of this gel was found to be 40 million times greater than its liquid counterpart, and it can be simplified in mounting and sealing. Moreover, the gel-electret obtained by charging this gel achieved a 24% increase in charge retention compared to the base material (i.e., alkyl-π liquid), due to the better confinement of electrostatic charges in the gel. The team then combined flexible electrodes with electret gel to create a vibration sensor. This sensor was able to detect vibrations at frequencies as low as 17 Hz and convert them to an output voltage of 600 mV, which is 83% higher than the voltage generated by the liquid alkyl-π electret sensor.

4. In future research, the team aims to develop wearable sensors that can respond to subtle vibrations and various strain deformations by further improving the characteristics of the charging electret (i.e., charge capacity and charge stability) and the strength of the alkyl-π gel. Furthermore, since this gel is recyclable and reusable as a vibration sensor material, its use is expected to help promote a circular economy.