A bionic PEEK composite structure with negatively charged surface adsorbing molecular brushes possessing improved biotribological properties for artificial joints

To improve the contact mode of artificial joints and their tribological performance, inspired by the ‘soft-on-hard’ structure of ‘cartilage-subchondral bone’ as well as negatively charged characteristic of the cartilage surface with brush-like molecules, a polyetheretherketone (PEEK)-hydrogel composite structure with negatively charged surface adsorbing cationic molecules through electrostatic interaction was designed and fabricated. Characterization results demonstrated that polyacrylic acid (PAA) hydrogel strengthened by polyvinyl alcohol (PVA) microcrystals was successfully fabricated on the PEEK substrate through ultra-violet (UV) radiation. Adsorption of cationic monomers was also confirmed. The PEEK-hydrogel composite structure had significantly reduced friction coefficient, ~80% lower than that of PEEK, owing to the synergistic effect of biphasic and boundary lubrication. This work proposes a novel route to develop the friction surface of artificial joints with advanced performance and contributes to the understanding of lubrication mechanism of artificial joints. •A PEEK-hydrogel-molecular brush composite for articular joints was prepared.•It had negatively charged surface adsorbing brushes mimicking natural joints.•Tribological performance of the composite was greatly improved compared to PEEK.•Lubrication mechanism of this system included biphasic and boundary lubrication.