A research team from the Universität Bayreuth and Aalto University in Finland has, for the first time, succeeded in developing a hydrogel with a unique structure that combines strength, flexibility and self-healing properties of natural skin. This breakthrough opens up new possibilities for applications such as targeted drug delivery, wound healing, sensors in soft robotics, and artificial skin.
Gels are an everyday presence – from soft, sticky substances like hair gel to jelly-like components in various foodstuffs. While human skin shares gel-like characteristics, it has unique qualities that are very hard to replicate. It combines high stiffness with flexibility and remarkable self-healing capabilities, often healing completely within 24 hours after injury.
Until now, artificial gels have either managed to replicate this high stiffness or natural skin’s self-healing properties, but not both. In a groundbreaking study, researchers at the University of Bayreuth embedded ultra-thin, specialized clay nanosheets with exceptionally large diameters into hydrogels, which are typically soft and elastic.
The synthetic clay nanosheets were designed and manufactured by Prof. Dr. Josef Breu. The result is a highly ordered structure with densely entangled polymers between nanosheets, not only improving the mechanical properties of the hydrogel but also allowing the material to self-heal.
In the manufacturing process, Chen Liang, a postdoctoral researcher at Aalto University, mixed a powder of monomers with water containing the nanosheets. The mixture was then exposed to UV light, which caused the individual molecules to bond, forming an elastic solid—a gel.
On the molecular level, the polymer chains are highly dynamic and mobile. When the material is cut, the chains begin to intertwine again. As a result, four hours after being sliced with a knife, the gel is already 80 to 90 percent healed. After 24 hours, it is typically completely repaired.
A one-millimeter-thick hydrogel contains 10,000 layers of nanosheets. This structure makes the material as stiff as human skin and gives it a comparable degree of stretch and flexibility. Achieving stiff, strong, and self-healing hydrogels has long been a challenge.
This new mechanism for reinforcing conventionally soft hydrogels could revolutionize the development of new materials with bio-inspired properties. It opens up new possibilities for targeted drug delivery, wound healing, sensors in soft robotics, and artificial skin.