Multi‐Walled Carbon Nanotube Reinforced Polyacrylamide‐Acrylic Acid Nanocomposite Hydrogels With Superior Mechanical and Tribological Performance as Focal Cartilage Substitute

ABSTRACT Though mimicking cartilage's structure, hydrogels often present weak mechanical performance, which limits their use in cartilage repair. Here, nanocomposite hydrogel was synthesized by incorporating multi‐walled carbon nanotubes (CNTs) into a covalently bonded polyacrylamide/polyacrylic acid (PAAm/PAAc) hydrogel. Fourier transform infrared and Raman spectroscopy confirmed CNT incorporation into PAAm/PAAc hydrogels, with scanning electron microscopy revealing homogenous CNT distribution. Swelling decreased, while the remaining mass increased, with higher concentrations of hydrophobic CNTs. Incorporating CNTs significantly increased the compressive modulus (0.094–0.299 MPa), comparable to articular cartilage. The average friction coefficient (COF) was lower in bovine calf serum (BCS) (0.16–0.20) than in phosphate‐buffered saline (0.22–0.26) due to the presence of plasma proteins, with CNT reinforcement reducing the COF by 25% in BCS compared to pristine hydrogel, indicating its suitability for cartilage repair. Under dry sliding, the COF drastically increased (0.55–0.65). CNT incorporation reduced wear volume by 36%‐61%, mainly attributed to effective load transfer by hard CNTs. Increased test load led to a 2.06–3.21‐fold increase in wear volume. SEM analysis revealed adhesion and abrasion as the primary wear mechanisms. PAAm/PAAc‐0.5CNT hydrogel demonstrated a superior balance of mechanical, tribological and biocompatibility properties. These findings confirm the merit of considering CNT‐incorporated PAAm/PAAc hydrogels as cartilage substitute.