Structure and antibacterial properties of Ag-doped micropattern surfaces produced by photolithography method

Photolithography methods offer ample opportunities for creating biological surface patterns over large areas. Herein, samples with patterned surface having the same Ag total coverage area and content, but different surface topography made of periodically spaced Ag/Si pillars with a diameter of 10 and 50 μm and a height of 3, 1, and 0.2 μm were produced by photolithography technique and studied to uncover the dependences of bactericide ion release on surface topography and antibacterial effect on Ag⁺ ion concentration. Reactive ion etching of Si wafers in areas unprotected by Ag capping layer was accompanied by a number of competing processes: (i) formation of Ag particles on the tops of pillars due to temperature-activated diffusion and coalescence, (ii) sputtering of Ag from the pillar to surface and redeposition into the etching cavities, resulting in the formation of small Ag nanoparticles located in areas between pillars, (iii) precipitation of AgSi_x phase as a result of chemical interaction of sputtered Si ions with Ag ions and atoms in surrounding plasma. Samples with the largest pillar heights which had also Ag particles formed between pillars demonstrated the fastest Ag⁺ ion release and, correspondingly, a noticeable antibacterial effect toward antibiotic-resistant hospital Escherichia coli K-261 strains already after 3 h. All samples showed 100% antibacterial effect after 24 h. Thus our results open up new possibilities for the production of scalable micropattern surfaces with controlled bactericide ion release and pronounced antibacterial characteristics for future applications in the orthopedic field.