Bio-Inspired Polymer Thin Films with Non-Close-Packed Nanopillars for Enhanced Bactericidal and Antireflective Properties

Abstract

The perpetual health and safety concerns caused by bacterial adhesion on surfaces demand the development of next-generation antibacterial materials. Inspired by bactericidal surfaces on cicada wings with protrusive nanostructures, which induce mechanical rupture of adhered bacterial membranes without antibacterial, chemical treatments, analogous structures have been fabricated on various synthetic materials to achieve such mechanical bactericidal efficacy. Herein, we developed a series of protrusive nanopillars on hard silicon (Si) substrates and soft poly­(ethylene glycol) diacrylate (PEGDA) thin films by colloidal lithography. We first investigated the correlation of interpillar distance and bactericidal efficacy against a model Gram-negative bacterium, Escherichia coli, using Si surfaces with different nanopillar number densities. We demonstrated that the bactericidal efficacy increased with decreasing nanopillar number density, which occurred when the average interpillar distance was smaller than the cell size. The bactericidal efficacy decreases when the average interpillar distance becomes larger than the comparable size of bacteria. We then designed PEGDA thin films with optimized bactericidal nanopillar density to improve their antibacterial and antireflective performance. The results indicate that the surface nanostructure plays a critical role in dictating antibacterial performance, regardless of the material type. This work provides insight into the understanding of physical interactions between nanostructured surfaces and bacterial cells as well as practical solutions for the development of antibacterial polymer surfaces for the application of optical lenses or screen displays to prevent public pathogenic infections.

Nanopillar Polymer Films as Antibacterial Packaging Materials

“…By contrast, assessment of the antibacterial efficacy of soft poly­(ethylene glycol) diacrylate (PEGDA) films with nanopillar height and diameter of 470 and 190 nm, respectively, but with varied packing density demonstrated that nanopatterns with reduced density (wider spacing) were more effective in reducing bacterial adhesion and led to greater bactericidal action toward E. coli (Table ). The most active surface pattern possessed nanopillars of h 478, d 186, and p 358 nm, respectively . Cui et al, determined that there was a critical nanopillar height required to kill E. coli cells on contact (∼200 nm).…”

“…The most active surface pattern possessed nanopillars of h 478, d 186, and p 358 nm, respectively. 49 Cui et al, determined that there was a critical nanopillar height required to kill E. coli cells on contact (∼200 nm). Additionally, surface patterns with smaller pillar cap diameter were more effective and the bacteria were also sensitive to pillar spacing.…”

Biofilms: Formation, Research Models, Potential Targets, and Methods for Prevention and Treatment

“…Synthetic replications of these nanopillars with different materials have shown potent bactericidal activity skin to dragonfly and cicada wings. [ 199 , 200 , 201 , 202 , 203 ] Sen et al fabricated sharp‐tipped nanostructures on silicon surfaces (NSS) utilizing the maskless deep reactive ion etching mimicking dragonfly wings (Figure 6D ). [ 204 ] Antimicrobial efficacy of the nanostructured surfaces coated with a thin layer of silver (NSS_Ag) or copper (NSS_Cu) was quantified.…”

Recent developments in antimicrobial and antifouling coatings to reduce or prevent contamination and cross‐contamination of food contact surfaces by bacteria

“…Another interesting type of antibacterial surfaces is those that physically destroy bacterial cell walls through the use of sharp, needle‐like nanoscale structures oriented normally to the substrate surface (Ivanova et al., 2012, 2013; Mohammadi Nafchi et al., 2014; Park et al., 2019; Podporska‐Carroll et al., 2015; Tan et al., 2020; Tripathy et al., 2017; Tsui et al., 2018). When bacterial cells adsorb onto surfaces with such sharp nanoscale features, the features perforate the bacterial cell walls.…”

“…Additionally, they can be difficult to produce on nonplanar substrate geometries, limiting their applications (Park et al., 2019). In order to mitigate these concerns, surfaces with these bactericidal needle‐like protrusion have been fabricated from flexible polymers such as patterned silicone, polymethylmethacrylate, polystyrene, poly (ethylene glycol) diacrylate, and poly(ethylene glycol) dimethylacrylate decorated with zwitterionic 2‐methacryloyloxyethyl phosphorylcholine (Park et al., 2019; Tan et al., 2020; Tripathy et al., 2017; Tsui et al., 2018). Fabrication of these polymer films with fine, needle‐like structure usually involves the molding of the films from a hard master made from a rigid material such as etched silicon.…”