In brief

Needle-like iron oxide 'nano-urchins' that can puncture microbial cell walls and membranes can be mixed into paint, paving the way for a new class of self-sanitizing surfaces.

© Yugen Zhang

Self-cleaning surfaces inspired by insects

27 Aug 2021

A*STAR scientists are developing the next generation of self-sanitizing surfaces by mimicking nanostructures on cicada wings.

The pandemic has heightened our anxiety about potentially pathogenic microorganisms lurking on shared surfaces in public areas. However, decontaminating everything may be doing more harm than good—the overuse of antibiotics and disinfecting agents is linked to the rise of anti-microbial resistance (AMR). Once acquired, AMR makes bacterial pathogens nearly invincible once they colonize surfaces, or worse, infect people.

To combat this emergent threat, researchers have begun looking to self-sanitizing surfaces in nature for inspiration. Insect wings are an excellent example: nanoscopic needle-like patterns on the surface of cicada and dragonfly wings destroy microbes physically instead of chemically, “popping” microbes that land on them.

Scientists have been able to mimic these natural biocidal nanostructures using zinc, gold, titanium, and silicon materials. However, these technologies aren’t scalable as Yugen Zhang, a Group Leader at A*STAR’s Institute of Bioengineering and Bioimaging (IBB), points out. “Most of the existing methods used for fabricating surface nanopatterns require special equipment, expensive starting materials, and specific substrates,” he said.

With funding support from the National Research Foundation’s Competitive Research Program, Zhang and his team devised ways of lowering existing barriers around manufacturing self-sanitizing nanostructure surfaces. To achieve this, they chose iron as an elemental building block due to its low cost, high abundance and environmentally inert properties.

First, the researchers designed chemical reactions for creating needle-like iron nanopillars on surfaces such as glass and tin under high heat and pressure conditions. Raising the temperatures in the reactors was found to generate a second type of iron nanopillar array, both of which exhibited strong ‘kill-by-structure’ properties, puncturing microbial cell walls and membranes.

Promisingly, these novel surface modification techniques were not limited to specific starting surface materials. Zhang and colleagues developed a method to synthesize self-standing ‘urchin’-shaped particles using the same iron compounds. These powders could then be applied as a coating to a wide range of materials, forming a protective biocidal outer layer. While coated surfaces were tough on bacteria, nano-urchin particles were found to be non-toxic and gentle on mammalian cells.

This innovation could soon be a chemical-free solution for limiting the spread of microbes in public spaces. “This technology could impose high-touch surfaces with long-term self-disinfection properties, either by creating surface nanostructures or by coating with nano-urchin particles,” said Zhang, who added that these particles could also simply be mixed into paint for direct application onto surfaces. The team now aims to prototype their discovery for commercialization.

The A*STAR-affiliated researchers contributing to this research are from the Institute of Bioengineering and Bioimaging (IBB) and the Singapore Institute of Manufacturing Technology (SIMTech).

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Yi, G., Teong, S.P., Liu, S., Chng, S., Yang, Y.Y., et al. Iron-based nano-structured surfaces with antimicrobial properties. Journal of Materials Chemistry B, 8, 10146 - 10153 (2020) | article

About the Researcher

Yugen Zhang is a Group Leader at A*STAR’s Institute of Sustainability for Chemicals, Energy and Environment (ISCE2). He earned his PhD in Chemistry from the University of Science and Technology of China (USTC) in 1992, subsequently joining its faculty and attaining professorship in 1999. He has served as a visiting scholar in Zhaomin Hou's group at Riken, Japan (1996-1997, 2000-2001) and was a postdoctoral research associate in R.H. Holm’s group at Harvard University (2002-2004). Specialising in green chemistry, nanomaterials and biomaterials, he has authored over 200 scientific papers and holds 50 patents.

This article was made for A*STAR Research by Wildtype Media Group