Mechanical and tribological properties of PVA/PAMPS/carboxylated CNT/mica nanocomposite hydrogel for novel bionic artificial cartilage

This study reports novel biomimetic polyvinyl alcohol (PVA) hydrogels modified with poly (2-acrylamido-2-ethylpropanesulfonic acid; PAMPS), mica and multi-walled carboxylated carbon nanotubes (CNTCOOH) and evaluates how filler identity and microstructure control functional properties for cartilage like applications. Spectroscopy and elemental mapping confirmed the presence and chemical integrity of all additives. Electron microscopy showed an interconnected porous network whose pore size increases with PAMPS, decreases with mica, and enlarges with CNTCOOH. Combining mica with CNTCOOH produced a denser network that strengthened the material but reduced fluid uptake. Measured water content (WC) ranged from 88.0% to 93.2%. The CNTCOOH rich composition swelled fastest and reached an equilibrium swelling ratio (SR) near 1692%, while the dual filler composition displayed limited swelling. Mechanical testing showed that the dual filler composition achieved the highest tensile strength (TS) of 0.55 MPa and the greatest elongation at break of 165% and also exhibited the highest compressive stiffness under large strain. In contrast, porous CNT rich samples absorbed fluid rapidly but had lower TS. Friction testing under joint like conditions identified hydration lubrication as the main low friction mechanism and the using both filler enriched samples produced the low coefficient of friction (COF) near 0.066. Wear tests after extended cycling revealed low average wear depths for the dual filler hydrogel and only minor surface flattening without cracking or delamination. Together these results demonstrate that deliberate choice and combination of fillers allow predictable tuning of swelling behavior, lubrication and mechanical resilience to meet different biomedical needs.