A breakthrough in material science has been made by researchers from Aalto University and the University of Bayreuth, who have developed a hydrogel that combines high stiffness with self-healing properties, similar to human skin. This new hydrogel could revolutionize fields such as drug delivery, wound healing, soft robotics, and artificial skin.
In a study published recently, the team added ultra-thin clay nanosheets to traditional hydrogels, which are usually soft and squishy. The result is a highly ordered structure with polymers densely entangled between nanosheets. This unique design enhances the hydrogel’s mechanical properties while allowing it to self-heal. The key to this innovation lies in the combination of the organized nanosheet arrangement and the entangled polymers between them.
The process behind the material’s creation is relatively simple. Postdoctoral researcher Chen Liang 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 and form a solid gel.
“The polymers twist around each other like tiny yarns,” said Hang Zhang, from Aalto University. “When fully entangled, the polymers become dynamic and mobile at the molecular level. If you cut them, they start to re-tangle and heal themselves.”
Just four hours after being cut, the material was 80 to 90 percent self-healed. After 24 hours, it was fully repaired. Remarkably, a one-millimeter-thick layer of the hydrogel contains 10,000 layers of nanosheets, giving it the same stiffness, stretch, and flexibility as human skin.
“This discovery addresses the challenge of creating strong, self-healing hydrogels,” said Zhang. “It could pave the way for developing new materials with bio-inspired properties.”
The team was inspired by biological materials, such as human skin, to design this unique hydrogel. “This work shows how nature can guide us in creating synthetic materials with new combinations of properties,” said Olli Ikkala, from Aalto University. “The results could lead to robots with self-healing skins or synthetic tissues that repair themselves.”
Although practical applications are still some way off, this breakthrough represents a major step forward in material design. The addition of ultra-large, thin clay nanosheets allows the hydrogel to achieve high strength while maintaining flexibility. Prof. Josef Breu, from the University of Bayreuth, explained that the key to the hydrogel’s strength is the uniform swelling of these nanosheets when in contact with water.
The project was led by Dr. Hang Zhang, Prof. Olli Ikkala, and Prof. Josef Breu, with the synthetic clay nanosheets designed and manufactured by Prof. Breu’s team.
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