Cicada-Wing-Inspired Nanopillar Hydrogels Consisting of Poly(vinyl alcohol) and Poly(methacrylic acid) for Capturing Bacteria through Their Flexibility and Wide Range of Motion

Abstract

The human race has learned about countering bacterial infection from other living organisms. In this study, cicada-wing-inspired hydrophilic nanopillars were prepared using commercially available porous alumina templates without the use of specialized equipment and additional materials. Hydrophilic polymers of poly­(vinyl alcohol) (PVA) and poly­(methacrylic acid) (poly­(MAAc)) were used to construct these nanopillars. The water-insoluble nanopillars formed by thermal cross-linking between the hydroxy and carboxy groups were highly flexible, with no significant structural disruption being observed on tilting them. The nanopillars captured Gram-negative and Gram-positive bacteria, despite their negatively charged surface leading an electrostatic repulsion with bacteria. The wing of the cicada has evolved to remain dry and maintain its lightweight. The water-containing cicada-wing structure may be an unknown encounter for bacteria and, thus, may become a countermeasure against the ever-changing bacteria.

Mechanobactericidal Nanotopography on Nitrile Surfaces toward Antimicrobial Protective Gear

“…Most of the reported studies in the scientific literature focused on hard materials such as silicon and metallic materials such as titanium and aluminum alloys. Recently, lethal damage and physiological changes to bacteria that are adhered to high-aspect-ratio nanostructured surfaces have been revealed. − Membrane cutting or stretching mechanisms are identified and caused by two categories of forces: (i) pressure exerted by the sharp nanostructures , and (ii) tension forces induced by the energy stored and released during the deformation of flexible nanostructures …”

“…A mask or mold with the desired dimensions of the target nanostructures is an essential first step. One of the techniques makes use of a commercially available anode aluminum oxide (AAO) template as a mask. , The plasma interacts with the substrate via the nanoscale opening of the AAO template and etches out the substrate. The nonexposed area transforms into insect-inspired nanopillars that remain on the substrate .…”

“…24 The polymer can be molded in the AAO template's nano-opening and replicated as nanoprojections on polymer surfaces. 6 Nanospheres can also be used as masks on a polymer substrate, with the exposed area between the nanospheres etched away by RIE. 25 Nanostructures resembling those on cicada wings can also be realized using hot embossing and UV nanoimprinting techniques.…”

“…However, there is limited research on mechanobactericidal nanostructures on polymeric materials. Recently, Ivanova et al fabricated 60 nm structures on poly­(ethylene terephthalate) and polypropylene to demonstrate antibiofouling properties for food packaging applications . However, polymers such as nitrile, commonly used for surgical gloves and aprons in healthcare applications, have yet to be investigated.…”

“…The nonexposed area transforms into insect-inspired nanopillars that remain on the substrate . The polymer can be molded in the AAO template’s nano-opening and replicated as nanoprojections on polymer surfaces . Nanospheres can also be used as masks on a polymer substrate, with the exposed area between the nanospheres etched away by RIE .…”