In our daily lives, we encounter various types of gels, found in products ranging from hair care to food, and even within our own bodies. However, human skin possesses unique properties that are challenging to replicate, seamlessly combining strength and flexibility. Perhaps most impressively, human skin has the remarkable ability to heal itself within just 24 hours of an injury. While artificially synthesized gels have achieved certain aspects of these qualities, a significant breakthrough has been made by scientists from Aalto University and the University of Bayreuth, who have developed a self-healing, flexible, and strong hydrogel, marking a crucial milestone in materials science.
The innovative hydrogel was created through the incorporation of ultra-thin clay nanosheets, which enabled the researchers to develop a rigid hydrogel that possesses enhanced properties. This dense entangled network of polymers not only strengthened the hydrogels, but it also ensured they did not become overly soft. Moreover, these nanosheets significantly improved the hydrogel's ability to self-repair. The research team mixed a powder of monomers with water containing the nanosheets, which was subsequently exposed to a UV lamp. According to Chen Liang, one of the authors of the study, “The UV radiation from the lamp causes the individual molecules to bind together so that everything becomes an elastic solid – a gel.”
The innovation's success heavily relies on the interactions between the polymers. Hang Zhang from Aalto University explains, “Entanglement means that the thin polymer layers start to twist around each other like tiny wool yarns, but in a random order. When the polymers are fully entangled, they are indistinguishable from each other. They are very dynamic and mobile at the molecular level, and when you cut them, they start to intertwine again.” This remarkable entanglement facilitates a rapid healing process, with the hydrogel achieving 80-90% repair within the first four hours of being cut, and complete restoration within 24 hours.
The hydrogel sample contains approximately 10,000 layers of nanosheets within just one millimeter of thickness, allowing it to achieve stiffness comparable to human skin while retaining the ability to stretch. Olli Ikkala from Aalto University notes, “This work is an exciting example of how biological materials inspire us to look for new combinations of properties for synthetic materials. Imagine robots with robust, self-healing skins or synthetic tissues that autonomously repair.” This fundamental discovery has the potential to redefine the rules of material design.
As further research and development continue, the applications of this self-healing hydrogel could extend to various fields, including medical materials that repair damage autonomously, flexible robots equipped with protective outer layers, and self-healing synthetic tissues. The possibilities are vast, shining a light on a future where materials mimic the remarkable healing powers found in nature.
