Graphene, an atom-thick layer of carbon, has been called a miracle solution for better batteries, stronger armour, flexible electronics, and more. Now a self-healing version could do even more.
Hongwei Zhu at Tsinghua University in China and his colleagues have made a graphene gel that is tough and rigid when dry, but squidgy, stretchy and self-healing when wet.
They mixed graphene sheets, just a nanometre thick, with water, then added polyacrylic acid, which has good water-absorbing properties. This created an interconnected network of graphene and acid, to which the team added calcium carbonate.
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The result was a soft black marble, like a tapioca ball. This stable gel is malleable when wet, making it soft enough to be extruded from a 3D printer, pressed into a mould, or twisted into a rope.
It dries out into a hard, plastic-like substance, strengthened by the added graphene, and can be formed into a solid shape, a thin film, or a foam, all with different potential applications, Zhu says. What is more, when the team cut a piece in half and placed the halves back together, they fused easily.
Gels like this have been made before, but the graphene is an added bonus, says Zhu. 鈥淕raphene is electrically and thermally conductive, which will introduce more functions for diverse applications.鈥�
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鈥淚t could be very useful,鈥� says Marek Urban at Clemson University in South Carolina. 鈥淵ou can change the shape, you can wet it and dry it, break it apart and stick it back together, you can do interesting things with it.鈥�
The team tested the material by building electrical circuits and weaving it with cotton fibres that could be used in wearable electronics. They also combined it with a magnet to create a tiny paper car driven by magnetic fields. Eventually, Zhu says, it could be used to make parts for a robot that could heal itself just by being tossed in the bath.
Advanced Materials
