Layered Hydrogel with Controllable Surface Dissociation for Durable Lubrication

Developing bioinspired hydrogel materials with extraordinary lubrication, load-bearing, and antiwear property is necessary for durable lubricious implants or devices. Despite the extensive research focus on lubrication of hydrogel materials, achieving a balance between lubrication and load-bearing for the current system is commonly difficult because of their poor mechanical property. Herein, a cartilage-inspired layered hydrogel material composed of a soft and porous top layer and a robust bottom layer is easily prepared by employing an alkali-induced network dissociation strategy. The thickness of the top soft layer increases with extending the alkali treatment time, along with differential surface and cross-sectional morphologies and mechanical property. The top soft and porous layer ensures that the surface shows extremely low friction (coefficient of friction (COF) ∼ 0.009, 3 N; COF ∼ 0.035, 20 N) against a hard steel ball contact pair, while the bottom layer acts as an excellent load-bearing function. Therefore, the layered hydrogels can achieve extraordinary wear resistance features, resulting from a combination of surface lubrication and bottom load-bearing. It is demonstrated that the method can be used to develop a layered hydrogel lubrication catheter, for which both of its inner and outer surfaces exhibit a slippery feature. The extraordinary lubricious performance of the layered hydrogels implies their potential application in the field of tissue engineering and medical devices.