Researchers at Aalto University, in collaboration with colleagues from the University of Bayreuth, have developed a hydrogel that closely replicates the mechanical behaviour of human skin. The material combines stiffness with flexibility and includes self-healing properties.
Hydrogels have tended to either achieve high stiffness or demonstrate self-healing characteristics, but rarely both. The novel method introduces large, ultra-thin clay nanosheets to the existing hydrogel infrastructure. The nanosheets arrange into an ordered structure as polymers form dense interlinked networks between them. The designed structure strengthens mechanical properties and gives the hydrogel the ability to self-repair after sustaining damage. This design not only enhances the mechanical properties but also enables the hydrogel to repair itself after damage. According to the research team, minor cuts in the material begin to close within hours and are fully restored within a day.
The collaboration was led by Dr. Hang Zhang, Prof. Olli Ikkala and Prof. Josef Breu and represents a collaborative effort by a dedicated team of researchers: Chen Liang, Volodymyr Dudko, Olena Khoruzhenko, Xiaodan Hong, Zhong-Peng Lv, Isabell Tunn, Muhammad Umer, Jaakko V. I. Timonen, Markus B. Linder. Their combined expertise has driven the breakthrough in developing a self-healing hydrogel with properties akin to human skin.
The synthetic clay nanosheets were designed and manufactured by Prof. Josef Breu at the University of Bayreuth in Germany. The research was published in Nature Materials and can be found below:
Liang, C., Dudko, V., Khoruzhenko, O., Hong, X., Lv, Z.-P., Tunn, I., Umer, M., Timonen, J. V. I., Linder, M. B., Breu, J., Ikkala, O., & Zhang, H. (2025). Stiff and self-healing hydrogels by polymer entanglements in co-planar nanoconfinement. Nature Materials. https://doi.org/10.1038/s41563-025-02146-5
The process involves mixing monomer powder with a nanosheet-infused water solution. Exposure to UV light then initiates polymerisation, binding the molecules into a gel-like structure. As explained by postdoctoral researcher Chen Liang, the UV treatment encourages the polymers to twist around each other in a way that resembles woven fibers. He stated:
“The UV-radiation from the lamp causes the individual molecules to bind together so that everything becomes an elastic solid; a gel,”
After the completion of full entanglement the polymer chains recover their natural bond reformation ability when cut. Each millimetre of two-dimensional material contains a total of 10,000 nanosheet layers because of its dense structure which enables both tensile strength and flexibility performance. Hang Zhang stated:
“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.”
Areas such as pharma (drug delivery), healthcare (Wounds), and the development of sensors for soft robotics could be improved by the results of this research. While practical applications are still in the developmental stage, the research offers a new framework for the design of bio-inspired materials.
Olli Ikkala of Aalto University emphasised that this work demonstrates how natural processes can guide the synthesis of new materials.
“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,”
he said, noting that the findings may influence future strategies in material design.
Hassan graduated with a Master’s degree in Chemical Engineering from the University of Chester (UK). He currently works as a design engineering consultant for one of the largest engineering firms in the world along with being an associate member of the Institute of Chemical Engineers (IChemE).
