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Tough Soft Wet Adhesion

Xuanhe Zhao's picture

Tough bonding of hydrogels to diverse non-porous surfaces

Hyunwoo Yuk, Teng Zhang,Shaoting Lin, German Alberto Parada & Xuanhe Zhao

Nature Materials (2015) doi:10.1038/nmat4463

A design strategy for tough bonding of hydrogels to diverse solids.

In many animals, the bonding of tendon and cartilage to bone is extremely tough (for example, interfacial toughness ~800Jm−2), yet such tough interfaces have not been achieved between synthetic hydrogels and non-porous surfaces of engineered solids. Here, we report a strategy to design tough transparent and conductive bonding of synthetic hydrogels containing 90% water to non-porous surfaces of diverse solids, including glass, silicon, ceramics, titanium and aluminium. The design strategy is to anchor the long-chain polymer networks of tough hydrogels covalently to non-porous solid surfaces, which can be achieved by the silanation of such surfaces. Compared with physical interactions, the chemical anchorage results in a higher intrinsic work of adhesion and in significant energy dissipation of bulk hydrogel during detachment, which lead to interfacial toughness values over 1,000Jm−2. We also demonstrate applications of robust hydrogel–solid hybrids, including hydrogel superglues, mechanically protective hydrogel coatings, hydrogel joints for robotic structures and robust hydrogel–metal conductors.




Zheng Jia's picture

Dear Xuanhe,

I enjoyed reading this paper a lot. I have a naive question regarding the fracture toughness of tough hydrogel. Does the inter-chain entanglements in hydrogel affect the fracture toughness? Fracture mechanics of bulk polymeric materials indicates that a increase in entanglement density facilitates the inter-chain stress transfer and thus enlarges the plastic zone size around the crack tip, leading to enhanced energy dissipation and fracture toughness. Does this mechanism also exist in hydrogels? Many thanks.

Best regards,

Xuanhe Zhao's picture

Dear Zheng,

Thanks for your interests in our work. Inter-chain entanglements indeed play a role in toughening hydrogels, similar to its toughening of elastomers. Owning to their soft wet nature, hydrogels are also amenable to many other toughening mechanisms. You may find a summary of these mechanisms here

Multi-scale Multi-mechanism Design of Tough Hydrogels: Building Dissipation into Stretchy Networks 



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