Researchers have created a unique hydrogel that is both tough and self-healing, thanks to nanosheet-enhanced polymer entanglements. The material, which can repair itself within hours, could revolutionize artificial skin, robotics and medical applications.
Gels can be found in everything from hair products to foods with a jelly-like texture. While human skin has some gel-like qualities, it's difficult to replicate. Skin is both stiff and elastic, and has an extraordinary ability to heal itself - often completely repairing it within 24 hours of injury.
Until now, artificial gels could only mimic skin's hardness or its ability to repair itself, but not both. A research team from Aalto University and the University of Bayreuth has now overcome this limitation. They have developed a hydrogel with a unique structure that combines strength and self-healing capabilities, paving the way for advances in drug delivery, wound healing, soft robotics and artificial skin.
In this groundbreaking study, researchers enhanced a hydrogel by adding ultrathin large clay nanosheets. Hydrogels are usually soft, but the new material forms a highly ordered structure with densely tangled polymers between nanosheets. This not only makes the hydrogel stronger, but also allows it to heal itself after damage.
The research was published today (March 7) in the prestigious journal Nature Materials.
The secret to this material lies not just in the ordered arrangement of the nanosheets, but also in the tangle of polymers between the nanosheets, and a process as simple as baking. Postdoctoral researcher Chen Liang mixed the monomer powder with water containing the nanosheets. The mixture is then placed under a UV lamp -- a styling lamp similar to gel nail polish. "The ultraviolet radiation from the UV lamp causes the individual molecules to bond together, turning everything into an elastic solid - a gel," Liang explained.
Aalto University's Zhang Hang added: "Entanglement means that thin polymer layers start to entangle with each other like tiny woolen yarns, but in a random order. When the polymers are completely entangled, they are indistinguishable from each other. They are very active and mobile at the molecular level, and when you cut them, they start to intertwine again."
Four hours after being cut with a knife, the material was already 80% or 90% self-healing. In addition, the one-millimeter-thick hydrogel contains 10,000 layers of nanosheets, which makes the material as stiff as human skin and has the same degree of stretch and flexibility.
"The stiffness, strength and self-healing properties of hydrogels have long been a challenge. We have discovered a mechanism that strengthens traditional soft hydrogels. This will revolutionize the development of new materials with bioinspired properties."
"This work is an exciting example of how biomaterials can inspire us to find new combinations of properties for synthetic materials. Imagine robots with durable, self-healing skin, or synthetic tissues capable of autonomous repair," said Aalto University's Olli Ikkala. Although practical applications may still be some way off, the current results represent a critical leap forward. This is a fundamental discovery that could update materials design rules.
Compiled from /scitechdaily