Microstructure-enhanced photothermal regulation for thermal management and antibacterial titanium surfaces

Photothermal therapy is an effective strategy for combating bacterial infections in diabetic-associated hostile microenvironments. However, existing photothermal systems are largely governed by intrinsic material properties, which limits the independent and scalable regulation of thermal behavior. Herein, we propose a microstructure-engineering strategy to achieve geometry-controlled photothermal regulation. Microgroove arrays with tunable spacing were fabricated on metallic substrates via wire electrical discharge machining (WEDM), followed by deposition of a conformal photothermal coating. By modulating light trapping, multiple reflections, and spatial heat confinement, the engineered microstructures enable photothermal performance to be regulated independently of the intrinsic properties of the coating material. Increasing groove density progressively enhances both heat generation and thermal retention. Among the investigated surfaces, the polydopamine (PDA)-coated Ti surface with a groove spacing of 100 μm (TSP100) exhibited the most favorable photothermal performance, characterized by rapid heating, enhanced heat retention, and stable thermal output. Under 808 nm near-infrared (NIR) irradiation, TSP100 produced a temperature increase of 23.6℃ and reached a maximum temperature of 47.6℃. Antibacterial performance was further evaluated in an in vitro high-glucose oxidative-stress microenvironment that simulated diabetic infection conditions. Under irradiation at 0.6 W/cm 2 for 10 min, TSP100 exhibits antibacterial efficiencies of 99.7% against Escherichia coli ( E. coli ) and 80.8% against Staphylococcus aureus ( S. aureus ), owing to the synergistic effects of photothermal heating and intracellular reactive oxygen species (ROS) generation. Moreover, the microstructured interface exhibits enhanced mechanical robustness and retains its photothermal functionality after abrasion, while maintaining favorable cytocompatibility and showing promising potential for inhibiting biofilm formation. This work establishes microstructure engineering as a programmable and generalizable strategy for photothermal regulation and provides a new framework for designing multifunctional antibacterial implants.