Engineers develop stretchable gel-based triboelectric nanogenerators for wearable technology

From smartwatches to fitness trackers to body-worn medical sensors, wearable devices are transforming the way we interact with technology. As their popularity increases, triboelectric nanogenerators (TENGs) that convert mechanical energy such as body movements into electrical energy offer a solution for powering these devices without the need for batteries.

Most TENGs used in portable applications incorporate a triboelectric material attached to an electrode that conducts current. However, one of the challenges has been finding flexible electrode materials that can move seamlessly with the human body.

To address these challenges, a research team led by Professor Jung Inn Sohn from Dongguk University, Seoul, Republic of Korea, developed a triboelectric nanogenerator based on gel polymer electrodes (GPE-TENG). This device is stretchable, semi-transparent and durable, making it suitable for wearable sensor applications. This paper was published in the Journal of Chemical Engineering on November 1, 2024.

“We report an in situ curing strategy aimed at developing stretchable, semi-transparent and durable GPE-TENG through improved interfacial bonding between ionic polymer gel and ecoflex layers,” explains Professor Sohn.

To make the device, the researchers poured a mixture of polyethylene oxide (PEO) gel and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) into an ecoflex mold. The gel is distributed evenly then covered with another ecoflex layer. A copper wire is attached to the gel for electrical connection, and the assembly is cured at 70°C for 12 hours, allowing the gel to bond strongly to the ecoflex layers.

The result is a durable, flexible, semi-transparent device that generates electrical signals when tapped or stretched, delivering a maximum power of 0.36 W/m² at a load of 15 MΩ. In testing, the device stretched up to 375% of its original size without damage and was able to withstand two months of bending, twisting, folding and stretching without any signs of delamination or loss of electrical performance.

As wearable technology becomes more and more a part of our daily lives, the proposed GPE-TENG could enable wearable devices to track joint activity for rehabilitation purposes or act as a biometric system in clothing, allowing users to unlock smart doors or lockers.

“This work could revolutionize wearable technology by developing durable and flexible electronic devices with promising applications in human healthcare, rehabilitation, security systemsand secure biometric authentication systems,” explains Professor Sohn.