Creation of a Power-Generating, Gel Electret-Based Device—Technology May Be Used to Develop Soft, Lightweight Wearable Motion Sensors for
Healthcare Purposes—
National Institute for Materials Science (NIMS)
Hokkaido University
Meiji Pharmaceutical UniversityAbstract
1. A team of researchers from NIMS, 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 withhighly 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 beused as a wearable healthcare sensor.
2. Interest in the development of soft, lightweight, power-generating materials has been growing in recentyears for use in soft electronics designed for various purposes, such as healthcare and robotics. Electretmaterials 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-temperaturealkyl–π liquid composed of a π-conjugated dye moiety and flexible yet branched alkyl chains (a type ofhydrocarbon compound). The alkyl–π liquids exhibit excellent charge retention properties, can be applied toother materials (e.g., through painting and impregnation) and are easily formable. However, when theseliquids have been combined with electrodes to create
flexible devices, they have proven difficult to immobilizeand seal, resulting in leakage issues. Moreover, theelectrostatic charge retention capacities of alkyl–π liquids
needed to be increased in order to improve their powergeneration capabilities.
3. The research team recently succeeded in creating analkyl–π gel by adding a trace amount of a low-molecularweight gelator to an alkyl–π liquid. The elastic storage
Figure. (a) Photographs of an alkyl–π liquid
modulus of this gel was found to be 40 million times thatand an alkyl–π gel in vials. (b) Response of anof its liquid counterpart, and it could be simplified fixation
alkyl–π gel-based vibration sensor to 17 Hz
and sealed. Moreover, the gel-electret obtained byvibrations.
charging this gel achieved a 24% increase in charge
retention compared to the base material (i.e., the alkyl–π liquid), thanks to the improved confinement ofelectrostatic charges within the gel. The team then combined flexible electrodes with the gel-electret to createa vibration sensor. This sensor was able to perceive vibrations with frequencies as low as 17 Hz and convert
them into an output voltage of 600 mV—83% higher than the voltage generated by an alkyl–π liquid electretbased sensor.
4. In future research, the team aims to develop wearable sensors capable of responding to subtle vibrationsand various strain deformations by further improving the charging electret characteristics (i.e., chargecapacity and charge life) and strength of the alkyl–π gel. Additionally, since this gel is recyclable and reusable
as a vibration sensor material, its use is expected to help promote a circular economy.
5. This project was carried out by a research team led by Akito Tateyama (Trainee, Frontier Molecules Group(FMG), Research Center for Materials Nanoarchitectonics (MANA), NIMS; also Student, Hokkaido
University-NIMS Joint Graduate School), Kazuhiko Nagura (Researcher, FMG, MANA, NIMS), Takashi
Nakanishi (Group Leader, FMG, MANA, NIMS) and Masamichi Yamanaka (Professor, Meiji PharmaceuticalUniversity).

Commented [A1]: 「π 共役色素部位」は、このように訳出しました。

6. This research was published in the online version of Angewandte Chemie International Edition on April 11,2024.

Contacts（Regarding this research）
Takashi NakanishiGroup Leader
Frontier Molecules Group
Research Center for Materials Nanoarchitectonics
National Institute for Materials Science
Tel: +81-29-860-4740
Email: NAKANISHI.Takashi[at]nims.go.jp
URL: https://www.nims.go.jp/funct_mol_g/（For general inquiries）
Public Relations Office
National Institute for Materials Science
Tel: +81-29-859-2026
Fax: +81-29-859-2017
Email: pressrelease[at]ml.nims.go.jp

Sohail Keegan Pinto (International Public Relations Specialist)
Public Relations & Communications Division
Office of Public Relations and Social Collaboration
Hokkaido University
Tel: +81-11-706-2186
Email: en-press[at]general.hokudai.ac.jp
Yasuhiro Takahashi
Public Relations Division
Meiji Pharmaceutical University
Tel: +81-42-495-8615
Email: koho[at]my-pharm.ac.jp2