Have you ever wondered what would happen if we cut off the skin of a robot? Probably nothing good, or at least that was the case until now. A team of researchers from theAalto University and University of Bayreuth has created something that is more reminiscent of a superpower than a scientific discovery: a “gel skin” capable of completely regenerating itself after being cut. A unique structure that combines rigidity, flexibility and self-healing capacity, just like our epidermis. The material, just four hours after the cut, it is already 80-90% healed, and after 24 hours the wound is completely healed. It's a discovery that could revolutionize fields ranging from robotics to regenerative medicine.
Strength lies in microscopic details
Gels are part of our daily lives, from hair sticks to gelatinous components of food. But until now, no artificial gel has managed to combine the high rigidity with the self-healing properties of human skin.
The real innovation of this gel skin lies in its microscopic structure. The team added exceptionally large and ultrathin clay “nanosheets” to the (normally soft and spongy) hydrogels, creating a highly ordered structure with densely woven polymers. A single millimeter of this material contains as many as 10.000 layers of nanosheets, giving it a rigidity comparable to human skin, with similar elasticity and flexibility.
It strikes me how something so technologically advanced is born from a process that, after all, has rather familiar elements: Hang Zhang from Aalto University mixes a monomer powder with water containing nanosheets, then exposes the mixture to a UV lamp (similar to the one used to set gel nail polish), and then the magic happens.
The intricate “dance” of molecules in gel skin
The secret of self-healing lies in what researchers call entanglement, a term that we often hear in quantum physics. This time, it's pure chemistry.
Entanglement means that the thin polymer layers begin to twist around each other like wool threads, but in a random order. When the polymers are completely entangled, they become indistinguishable from each other. They are very dynamic and mobile at the molecular level, and when you cut them, they begin to entangle again.
Chen Liang, a postdoctoral researcher involved in the study, explains that “the UV radiation from the lamp causes the individual molecules to bind together so that the whole thing becomes an elastic solid: a gel.” Simple, isn't it?
Beyond the imitation of nature
Research, published in the prestigious magazine Nature Materials, represents one of those conceptual leaps that could change the rules of materials design.
Olli Ikkala, from Aalto University, already sees the future implications:
Imagine robots with tough, self-healing skin, or self-repairing synthetic fabrics.
The synthetic clay nanosheets were designed and manufactured by Prof. Josef Breu of the University of Bayreuth in Germany, while the Aalto researchers used the facilities of the Nanomicroscopy Center, part of the Finnish national research infrastructure OtaNano. It is precisely this international collaboration that has made it possible to overcome limits that seemed insurmountable: rigid, strong and self-healing hydrogels have long been an unsolved challenge.
What now? Gel skin could be just the beginning of a new generation of biomimetic materials. I can't wait to get my hands on (that's the right word) robots with skin that behaves like ours. And I hope I don't get slapped after a pinch. Or a kung fu punch.
