Imagine a future where your clothes power your devices and recognize you with a simple tap. Researchers at Dongguk University have developed a gel polymer-based triboelectric nanogenerator that generates electrical signals from body movement to power electronics like LEDs and functions as a self-powered touch panel for user identification. The device can stretch up to 375% of its original size and withstand rigorous mechanical deformations, making it suitable for wearable applications.

From smartwatches, and fitness trackers to medical sensors that can be worn on the body, wearables are transforming the way we interact with technology. As their popularity grows, triboelectric nanogenerators (TENGs) that convert mechanical energy such as body movement to electrical energy offer a solution to power these devices without relying on batteries.

Most TENGs used in wearable 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 in the Republic of Korea developed a gel polymer electrode-based triboelectric nanogenerator (GPE-TENG). This device is stretchable, semi-transparent, and durable, making it suitable for wearable sensor applications. This paper was made available online on 11 Oct 2024 and was published in Volume 499 of the Chemical Engineering Journal on 1 Nov 2024.

“We report an in-situ curing strategy to develop a stretchable, semi-transparent, and durable GPE-TENG through enhanced interfacial bonding between the ionic polymer gel and ecoflex layers,” explains Prof. Sohn.

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

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

As wearable technology becomes a bigger part of our daily lives, the proposed GPE-TENG could enable wearable devices that 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 sustainable and flexible electronic devices with promising applications in human healthcare, rehabilitation, security systems, and secure biometric authentication systems,” says Prof. Sohn.

Title of original paper: In-situ cured gel polymer/ecoflex hierarchical structure-based stretchable and robust TENG for intelligent touch perception and biometric recognition

Journal: Chemical Engineering Journal

DOI: 10.1016/j.cej.2024.156650

Dongguk University, founded in 1906 by the Jogye Order of Korean Buddhism, is a premier Buddhist institution of higher learning. Originally established as Myeongjin School, it is rooted in Buddhist principles, Korean tradition, and historical significance. With a legacy of empowering approximately 350,000 professionals instrumental in Korea’s modernization and democratization, the university continues to cultivate future leaders who shape the world while advancing Korean Buddhism, guided by its motto: “The revival of Buddhism fuels Dongguk’s growth, and vice versa.”

Dr. Jung Inn Sohn is currently a Professor in the Division of Physics and Semiconductor Science at Dongguk University, Korea. His research group focuses on developing new low-dimensional materials and exploring their fundamental physical properties and new functions for potential applications in energy and optoelectronics. He was formerly a faculty member at the University of Oxford and a senior researcher at Samsung Advanced Institute of Technology and the University of Cambridge. His research is described in more than 175 SCI articles in top journals including Nature, Nature Communications, Energy & Environ. Sci., as well as 21 cover picture articles and 4 review articles. He has an h-index of 47 and 30 patents to his name.