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An Anti-Freezing Organohydrogel for Human-Machine Interactive Devices

Scientists have developed an anti-freezing organohydrogel that could pave the way for more anti-freezing soft materials that work efficiently at subzero temperatures.

In today’s hyperconnected society, human-machine interaction has become crucial for mobile communications, humanoid robots, and intelligent medical apparatus and instruments. Current human-machine interactive devices, such as keyboards and touch panels, are made from rigid or brittle materials that render them unwearable. There is a need to develop the next generation of flexible human-machine interactive devices that are soft, stretchable, and preferably self-powering.

Scientists led by Professor Chen Tao at the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences have developed an anti-freezing organohydrogel that was used to prepare triboelectric nanogenerators (TENGs), realising high-efficiency human-machine interaction at -30 degrees Celsius.

Ionic conductive polymer gels, like organohydrogels, have adjustable mechanical properties and electrical conductivity, which has been utilised to develop soft and stretchable sensors to be incorporated into wearable human-machine interactive devices.

In nature, many organisms can survive under extremely cold environments by preventing the formation of ice crystals in cells. They accumulate cryoprotectants, like urea and glucose, in tissues to bring down the freezing point of bodily fluids. Inspired by such anti-freezing organisms like the tree frog, the scientists at NIMTE developed an anti-freezing organohydrogel made up of polyacrylamides/nano-clays networks absorbed with ethylene glycol/water.

Prof. Chen and colleagues prepared the organohydrogel through solvent replacement of a hydrogel in ethylene glycol/water and the hydrogel is synthesised through in-situ polymerisation of the monomer acrylamide in aqueous solution of nano-clays. Then, the organohydrogel was used as electrodes to prepare organohydrogel TENGs, which were further attached on fingers as self-powered sensors to develop human-machine interactive keyboards.

Pulse voltage signals were collected and converted to letters and punctuations for display on a monitor. Through this, the team successfully demonstrated the use of a self-powered flexible keyboard at -30 degrees Celsius.

The team’s work demonstrate the exciting potential of organohydrogels, TENGs, and human-machine interactive systems that could translate into the development of anti-freezing soft materials, self-powered sensors, and unobtrusive surveillance communicators at subzero temperatures. [APBN]

Source: Xu et al. (2021). Anti-freezing organohydrogel triboelectric nanogenerator toward highly efficient and flexible human-machine interaction at− 30° C. Nano Energy, 90, 106614.