Durable bionic hydrogels nanocomposite with cartilage-mimetic charge: Tailoring tribological and mechanical properties with functionalized carbon nanotubes for artificial cartilage

Advances in understanding natural articular cartilage have led to the development of bionic repair materials, with hydrogel composites emerging as a promising option due to their low friction, high water content, and customizable mechanical properties. This study investigates PVA/PAMPS/FMWCNT hydrogels, focusing on the role of negatively charged groups in enhancing performance. FTIR analysis confirmed the integration of PVA, PAMPS. SEM revealed a porous structure resembling cartilage, with carboxyl-functionalized samples showing the largest pores and achieved a 1853% swelling ratio, while hydroxyl- and amine-functionalized samples had smaller pores and greater crosslink density. Mechanical tests showed hydroxyl-functionalized samples achieved 1.01 MPa tensile stress and 237% elongation, whereas carboxyl-functionalized samples, despite strong hydrogen bonding, had inferior mechanical properties due to high porosity. Tribological tests demonstrated carboxyl-functionalized samples had the 0.0346 coefficient of friction (COF), attributed to their high negative charge density and hydration lubrication. Long-term friction tests revealed a stable coefficient (0.07), demonstrating sustained frictional stability under extended sliding conditions. These findings highlight the importance of functionalized multiwall carbon nanotubes (FMWCNT) and negatively charged groups in optimizing hydrogels for cartilage repair, offering insights for developing bionic materials.