Recently, joint research from Aalto University and the University of Bayreuth successfully developed a revolutionary new hydrogel that not only has strength and flexibility comparable to human skin but also has amazing self-healing ability. This research result was published in the top journal Nature Materials on March 7, bringing unprecedented opportunities in the fields of drug delivery, wound healing, soft robot sensors, and artificial skin.

In daily life, we often come into contact with various gels, from soft and sticky substances in hair care products to jelly-like ingredients in food. However, the gel-like characteristics of human skin have unique properties that are difficult to replicate: it is both hard and flexible, and it can usually heal completely within 24 hours after injury. For a long time, artificial gels have been unable to achieve these properties at the same time. However, this latest research has finally broken through this limitation.

The research team created a new type of hydrogel with a unique structure by adding ultra-large and ultra-thin special clay nanosheets to the usually soft and elastic hydrogel. This highly ordered structure allows tightly entangled polymers between the nanosheets, which not only significantly improves the mechanical properties of the hydrogel but also gives it the ability to self-heal.

In introducing the breakthrough, postdoctoral researcher Chen Liang said the process is quite simple: just mix the monomer powder with water containing the nanosheets and then shine the mixture under an ultraviolet lamp, similar to the lamp used to fix gel nail polish. The ultraviolet light causes the individual molecules to bind together to form an elastic solid - a gel.

The secret of this new hydrogel lies in the orderly arrangement of nanosheets and the polymers entangled between them. When the polymers are fully entangled, they become very dynamic and mobile at the molecular level. Therefore, when the material is cut, the polymer layers begin to intertwine again like tiny wool yarns, achieving self-repair. Experimental results show that four hours after cutting with a knife, the material can already self-repair 80% to 90%, and can usually be completely repaired after 24 hours.

Even more amazing is that this one millimeter thick hydrogel contains 10,000 layers of nanosheets, making it as hard as human skin, while also being stretchable and flexible. "Hydrogels that are hard, strong, and self-healing have always been a challenge. We have discovered a mechanism to strengthen traditional soft hydrogels, which could revolutionize the development of new materials with biomimetic properties," said Professor Hang Zhang from Aalto University.

This research not only shows how biological materials can inspire us to find new combinations of properties in synthetic materials but also provides endless possibilities for future applications. Professor Olli Ikkala from Aalto University said: "Imagine robots with strong, self-healing skin or synthetic tissues that repair themselves. Although there may be some way to go before practical applications, the current results represent a key leap forward, a fundamental discovery that can update the rules of material design."

The collaboration was led by Dr. Hang Zhang, Professor Olli Ikkala and Professor Josef Breu. The synthetic clay nanosheets were designed and manufactured by Professor Josef Breu of the University of Bayreuth in Germany. This breakthrough research result has undoubtedly opened up new research directions in the field of materials science and provided a solid foundation for future technological innovation.