Researchers have developed first synthetic skin that is both sensitive to touch and capable of healing itself quickly and repeatedly at room temperature.
The finding could lead to smarter prosthetics or resilient personal electronics that repair themselves.
Stanford University Professor Zhenan Bao and her team have succeeded in making the first material that can both sense subtle pressure and heal itself when torn or cut.
In the last decade, there have been major advances in synthetic skin, said Prof. Bao, but even the most effective self-healing materials had major drawbacks.
Some had to be exposed to high temperatures, making them impractical for day-to-day use.
Others could heal at room temperature, but repairing a cut changed their mechanical or chemical structure, so they could only heal themselves once.
Most importantly, no self-healing material was a good bulk conductor of electricity, a crucial property.
“To interface this kind of material with the digital world, ideally you want them to be conductive,” said Benjamin Chee-Keong Tee, first author of the study.
The researchers succeeded by combining two ingredients to get what Prof. Bao calls “the best of both worlds”, the self-healing ability of a plastic polymer and the conductivity of a metal.
They started with a plastic consisting of long chains of molecules joined by hydrogen bonds - the relatively weak attractions between the positively charged region of one atom and the negatively charged region of the next.
“These dynamic bonds allow the material to self-heal,” said Chao Wang, a co-first author of the research.
The molecules easily break apart, but then when they reconnect, the bonds reorganise themselves and restore the structure of the material after it gets damaged, he said.
The result is a bendable material, which even at room temperature feels a bit like saltwater taffy left in the fridge.
To this resilient polymer, the researchers added tiny particles of nickel, which increased its mechanical strength.
The nanoscale surfaces of the nickel particles are rough, which proved important in making the material conductive.
Researchers took a thin strip of the material and cut it in half with a scalpel.
After gently pressing the pieces together for a few seconds, the researchers found the material gained back 75 per cent of its original strength and electrical conductivity. The material was restored close to 100 percent in about 30 minutes.
“Even human skin takes days to heal. So I think this is quite cool,” Mr. Tee said in a statement.
The study findings were published in the journal ‘Nature Nanotechnology’.