Antibacterial effects of the artificial surface of nanoimprinted moth-eye film

Abstract

The antibacterial effect of a nanostructured film, known as “moth-eye film,” was investigated. The moth-eye film has artificially formed nano-pillars, consisting of hydrophilic resin with urethane acrylate and polyethylene glycol (PEG) derivatives, all over its surface that replicates a moth’s eye. Experiments were performed to compare the moth-eye film with a flat-surfaced film produced from the same materials. The JIS Z2801 film-covering method revealed that the two films produced a decrease in Staphylococcus aureus and Esherichia coli titers of over 5 and 3 logs, respectively. There was no marked difference in the antibacterial effects of the two surfaces. However, the antibacterial effects were reduced by immersion of the films in water. These results indicated that a soluble component(s) of the resin possessed the antibacterial activity, and this component was identified as PEG derivatives by time-of-flight secondary ion mass spectrometry (TOF-SIMS) and Fourier transform infrared spectroscopy (FT-IR). When a small volume of bacterial suspension was dropped on the films as an airborne droplet model, both films showed antibacterial effects, but that of the moth-eye film was more potent. It was considered that the moth-eye structure allowed the bacteria-loaded droplet to spread and allow greater contact between the bacteria and the film surface, resulting in strong adherence of the bacteria to the film and synergistically enhanced bactericidal activity with chemical components. The antibacterial effect of the moth-eye film has been thus confirmed under a bacterial droplet model, and it appears attractive due to its antibacterial ability, which is considered to result not only from its chemical make-up but also from physical adherence.

Multifunctional Coatings and Nanotopographies: Toward Cell Instructive and Antibacterial Implants

“…Sharper, more closely packed nanopillars were more effective, possibly because bacteria on these surfaces both contacted more nanopillars and experienced higher stresses at these contact points, which was in agreement with that found in different insect species . Replication of moth eye‐like nanopillars/cones via nanoimprinting also demonstrated good bactericidal performance in both dry and wet conditions, which could potentially be used for inhibiting nosocomial infections or any sanitation‐conscious touching surfaces. Hazzel et al produced similar nanopillar/cone surfaces using colloidal microbeads as masks followed by RIE.…”

“…Inspired by nature, a number of studies have since been carried out to develop bactericidal nanotopographies on synthetic materials. They include silicon and diamond coated silicon, titanium and its alloy, polymers, stainless steel, and aluminium . Table 3 lists a summary of biomimetic bactericidal surfaces on various materials currently in development.…”

Antibacterial effects of nanoimprinted moth-eye film in practical settings

“…1. For Firstly, immediaye effectivity of Moth-eye was considered that nanostructure with hydrophilic resin enhanced the antibacterial effect, which was reported in our previous in vitro study [9]. Furthermore, the superhydrophilic property of Moth-eye leads to a quick drying of water droplets that adhere to the moth-eye surface.…”

“…The resulting film possesses unique nanostructure arrays that exhibit a variety of useful functions, including super-hydrophilic or super-hydrophobic properties due to the larger surface area of the moth-eye film compared to a flat surface. In previous work, we reported that our moth-eye film exhibited enhanced antibacterial effects in in vitro experiments [9]. However, the moth-eye film has not been evaluated for antibacterial effects in practical environments.…”

“…The arrangement of sample species were changed for each test in order to prevent the number of collecting colonized from being influenced from the pasting place. To adjust the test start time, after laminating, each of the 9 sample film surfaces and each sinks were disinfected by wiping three times with an ethanol-impregnated paper cloth, and that time was taken as the start time of each tests.…”