Nanopillared Polycarbonate Surfaces Having Variable Feature Parameters as Bactericidal Coatings

The harm of a global rise in the biofilms formation caused by bacteria adhering to surfaces calls for the design and fabrication of a generation of bactericidal materials. Recently, much inspiration has been drawn from naturally occurring mechano-bactericidal surfaces with physical structures such as cicada wings in fabricating their synthetic analogues. Here, we fabricated a series of the highly controllable nanometer-scale characteristic polycarbonate (PC) surfaces using anodic aluminum oxide template-assisted hot embossing and wet etching. The influences of geometric parameters of PC nanostructured surfaces, including the height, diameter, and interspacing, which can be adjusted independently, on the bactericidal efficiency were systematically investigated. Our experimental results demonstrate that, for the surfaces able to kill bacteria, there is a critical height of nanostructures required, similar to 200 nm; the smaller the cap diameter of nanopillars, the greater the pressure exerted on bacterial cell by nanopillars, namely, the cell is likely to be destroyed; bacteria are also sensitive to interpillar spacing. It is possible that an optimal range of interpillar spacing on nanostructured surface will result in its high bactericidal activity. In this work, the highest bactericidal rates (98.4% for Escherichia coli) were obtained from the nanostructured surfaces with above 200 nm of height, less than 60 nm of cap diameter, and 170 nm of interpillar spacing.