(135c) The Effect of Mechanical Property of Nanostructured Polymer Thin Films on the Surface Tension-Driven Bactericidal Efficacy

Natural surfaces with protrusive nanostructures have been highlighted because of their ability to physically and mechanically damage attached bacteria. Biomimetic nanostructures created on hard, inorganic materials with high Young’s moduli, such as silicon or stainless steel, have exhibited high bactericidal efficacy through mechanical membrane rupture, caused by the force generated from the surface tension or interfacial energy gradient. Comparatively, less is known about soft polymers despite their prevalent usage in biomedical and food industries that require antibacterial surfaces. We hypothesized that the deformation of soft nanostructures fabricated on polymer thin films could occur upon bacterial adhesion, which would reduce the force necessary to rupture the bacterial membrane. To test this hypothesis, we developed protrusive nanostructured thin films with different Young’s moduli ranging from tens to hundreds of MPa by varying polymer molecular weights and crosslinking densities. We created the same surface nanostructure on polymer thin films with differing stiffnesses by a soft molding pattern transfer method and investigated the correlation of polymer stiffness and bactericidal efficacy against both Gram-positive and Gram-negative bacteria. The stiffness of the nanostructured polymer thin films dictated the sensitivity in the bactericidal efficacy depending on the size, shape, and type of the bacterial strains tested, suggesting rational design parameters for surfaces to kill target bacteria utilizing surface tension. This work improves our understanding on the role of mechanical properties of the surface nanostructure in determining bactericidal efficacy. Additionally, the versatile fabrication methods used in this work provide practical insight into the development of bactericidal, medical surfaces made from diverse polymers by engineering their surface structure and mechanical properties.