A Janus hydrogel material with lubrication and underwater adhesion

Double-layer hydrogel materials combine excellent hydrophilicity, outstanding lubricating properties, high load-bearing modulus, and good biocompatibility, and are often used to achieve high load-bearing (high modulus) and low frictional (low modulus) properties of articular cartilage, but which also makes it difficult for them to form efficient, stable and long-term adhesion underwater. Herein, we constructed a kind of novel underwater Janus hydrogel patches with strong adhesion performance by robustly anchoring mussel-protein-inspired poly (dopamine methacrylamide-co-methoxyethyl acrylate) p(DMA-co-MEA) copolymer onto the surface of poly(acrylic acid-co- acrylamide) p(AAc-co-AAm) hydrogel with bilayer modulus structure analogous to articular cartilage. Due to the coupling of the top lubrication layer and the bottom load-bearing layer, the constructed Janus hydrogel patch not only has fatigue resistance and low friction but also high load-bearing [coefficient of friction (COF) ∼0.0076, 5 N; COF∼0.048, 30 N]. Moreover, the Janus hydrogel also exhibits excellent bonding strength underwater (bonding strength ∼41.6 kPa, Fe substrate). Our strategy for constructing a novel underwater Janus hydrogel patch will provide valuable guidance for the realization of interface bonding of soft material of bionic articular cartilage and promote the practical application of tissue engineering.