Laser-Engineered Black TiO₂/UHMWPE Nanocomposites: Tribomechanical Response and Potential for Biomedical Bearing...

Wear of ultra-high-molecular-weight polyethylene (UHMWPE) remains a limitation for long-term orthopedic bearing performance. This study investigated how pulsed laser irradiation in liquid (PLIL)-induced modification of TiO₂ affects the mechanical and tribological response of UHMWPE nanocomposites containing 0.1-1.0 wt% TiO₂. PLIL changed TiO₂ from predominantly irregular/angular particles with an anatase-dominant composition (~56% anatase/44% rutile) to a greater prevalence of rounded particles with a rutile-dominant balance (~41% anatase/59% rutile). TiO₂ incorporation produced a statistically significant but moderate microhardness increase, reaching 4.19 ± 0.12 HV0.05 at 1.0 wt% untreated TiO₂, approximately 25% above neat UHMWPE. Tribological behavior was formulation dependent: 0.5 wt% PLIL-modified black TiO₂ exhibited the lowest mean wear volume (2.06 ± 0.02 mm³), 13.1% below neat UHMWPE (2.37 ± 0.23 mm³), although the difference was not statistically significant (p = 0.739). Maximum microhardness, minimum terminal friction, and minimum mean wear occurred in different formulations, demonstrating that these responses are partially decoupled. Nanoparticle state and concentration jointly governed the tribomechanical response within the investigated low-filler regime.