A coating with hydrogel@nanostructure on Ti surfaces via controllable Nano-mechanical interlocking

The elasticity mismatch between Ti and tissue limits the performance of Ti medical devices. How to create a coating with mimicking natural soft tissue stiffness and possessing strong mechanical bond is a challenge in implant manufacturing. Here, we developed a combined coating, that is, an anodized Ti surface (ATS) with nanostructures coated with a layer of PAAm hydrogel with tunable elasticity. Due to the nano-mechanical interlocking and hydrogen bonding synergy, the PAAm hydrogel layer was tightly anchored in nanostructures on the ATS. By regulating the oxidation voltage, nanostructures including nanopores, nanotubes, and punch-through nanotubes were fabricated on the ATS, and these three kinds of anodized nanostructures increase the porosity of the ATS sequentially. The lap shear test has shown that the shear strength increases linearly with increasing the porosity, and the shear strength of the punch-through nanotube structures with the PAAm hydrogel coating reaches 59.28 kPa. The adhesion mechanism between the anodized Ti nanostructures and the PAAm hydrogel coating is mainly due to the nano-mechanical interlocking and hydrogen bonding synergy, which was proven by morphology analysis, XRD, and ATR-FTIR characterization of the samples subjected to lap shear load. The hydrogel-nanostructures coating has demonstrated the potential to be applied in Ti medical devices.