A new hydrogel material for next-generation integrated touchscreens

August 11, 2022

(News from Nanowerk) Many touch screens today are based on indium tin oxide and face various limitations due to their brittle and rigid nature. However, given the rapid advances in artificial intelligence and the Internet of Things, researchers have devoted considerable effort to exploring new materials for next-generation integrated touchscreens with multi-functionalities such as transparency, extensibility, flexibility and self-healing capacity.

For example, there have been a growing number of reports of next-generation hydrogel-based touchscreens. The latest development, reported in Advanced functional materials (“Anti-freeze self-adhesive self-healing degradable touchscreen with ultra-stretch performance based on transparent triboelectric nanogenerators”) was an antifreeze degradable triboelectric nanogenerator (AD-TENG) with high electrical output property using a novel biocompatible zwitterionic network hydrogel as a transparent self-adhesive self-healing ion conductor with ultra-stretch performance.

Here, researchers from Harbin Institute of Technology designed and fabricated a transparent AD-TENG by sandwiching the zwitterionic network hydrogel with two layers of PDMS using the hydrogel as a current collector. When a hand comes in contact with the AD-TENG, tribo-electrification occurs at the interface and triboelectric charges of opposite polarities are generated on the surface of the PDMS and the skin, respectively. The hydrogel can adhere to different targeted substrates and instantly regain its initial conductivity upon damage due to the existence of polar zwitterion groups.

Structural diagram of the AD-TENG. (Adapted with permission from Wiley-VCH Verlag)

The result is triboelectric nanogenerator technology to realize the self-powering capability of flexible electronics. In their report, the team demonstrated that their self-powered system has strong energy harvesting capability with remarkable stability, which could light up a serial LED array and directly drive wearable electronics even at large strain. and in a low temperature environment.

In addition, they also demonstrated the design of an eco-friendly wearable epidermal touch screen with flexible and multi-functional properties on curved human skin. They have successfully used this touch screen both in the initial state and in the self-healing state for various operations including writing and playing computer games even in low temperature environment. .

Structure and operation of an epidermal touch screen Structure and functioning of an epidermal touch screen. a) Schematic illustration of an epidermal integrated touch screen. b–d) Operational photographs of the reading of Angry Birds by an epidermal touch screen. b) an Angry Bird was caught by the slingshot when a finger touched the panel, c) the slingshot was released when the finger left the panel and the bird took off, d) the target was broken by the ‘bird. e–g) Record photographs of playing chess using the panel. e) a chess piece was selected when the finger clicked on the position of the piece on the touchscreen, f) another chessboard position was chosen for the chess piece and the chess piece has been moved, g) the chess piece has been moved to the target position. (Reproduced with permission from Wiley-VCH Verlag)

The researchers believe that this work not only provides a practical way to build human-machine communication interfaces with a self-powered nature, but will also shed new light on the design of promising materials for flexible electronics, such as actuators. , soft robotics and electronic skins.

Irene B. Bowles