Biomimetic Layered Hydrogel Coating for Enhanced Lubrication and Load-Bearing Capacity

Biomimetic hydrogel lubrication coatings with high wettability and low friction show great promise in tissue engineering, wound dressing, drug delivery, and intelligent sensing. Inspired by the hierarchical structure of natural cartilage, a layered hydrogel coating was constructed to functionalize rigid polyetheretherketone (PEEK). The layered hydrogel coating features a structural design comprising a top soft layer and a middle robust layer. The porous structure of the top soft hydrogel layer stores water molecules, providing surface lubrication, while the dense structure of the middle robust hydrogel layer offers load-bearing capacity. These synergistic effects of the gradient hydrogel layer endow the PEEK substrate with an ultra-low coefficient of friction (COF~0.010 at 5 N load), good load-bearing capacity (COF~0.031 at 10 N load), and excellent wear resistance (COF < 0.05 at 5 N load after 20,000 sliding cycles). This study introduces a novel design paradigm for robust hydrogel coatings with exceptional lubricity, displaying the potential application in cartilage replacement materials.