Antibacterial chitosan/ZnO composite coatings with femtosecond laser-induced micropatterned surfaces

This study reports a chitosan (CS)-based antibacterial composite coating with engineered surface functionality achieved through ZnO incorporation and femtosecond laser-induced micropatterning. Triangular micropatterns with pitch ranging from 30 to 120 μm were fabricated on polystyrene (PS) molds via femtosecond laser ablation and subsequently transferred onto CS composite coatings by solution casting. The coatings consisted of CS, glycerol (Gly), and glutaraldehyde (GA), with or without the addition of 1.5 wt% ZnO microparticles, enabling independent control of composition and surface microstructure. Surface characterization indicated that ZnO incorporation modified the chemical environment of the CS matrix, while laser-induced micropatterns altered surface morphology and wettability. Antibacterial performance was evaluated against Escherichia coli ( E. coli ) and Streptococcus gordonii ( S. gordonii ). ZnO-containing flat films reduced bacterial density, reaching 83% for E. coli and 77% for S. gordonii , respectively, whereas micropatterned films without ZnO achieved moderate reductions (32% and 34%) due to surface-mediated anti-adhesion effects. Notably, the combination of ZnO incorporation and micropatterning further enhanced antibacterial performance, yielding reductions of up to 93% for E. coli at a 30 μm pitch and 90% for S. gordonii at a 120 μm pitch. Three-way analysis of variance (ANOVA) confirmed that ZnO incorporation, micropattern pitch, and bacterial species all exert statistically significant effects on bacterial adhesion behavior. The results demonstrate that integrating ZnO fillers with controlled surface microstructures provides an effective strategy for tailoring antibacterial performance in polymer-based composite coatings. This scalable, low-temperature fabrication approach offers potential for applications in functional coatings, packaging materials, and biomedical surfaces.