The Engineer

New anti-bacterial surfaces could be made possible by replicating the surface of a butterfly wing, EPSRC-funded scientists from Bradford University have reported.

The technology could be applied to hip and other joint replacements, cosmetic and orthodontic products, and be used in the car industry.

The team has created a series of laser-textured nano-moulds to replicate the butterfly wing pattern. When viewed under a microscope, butterfly wings exhibit a unique ‘ladder’ design that prevents bacteria from establishing colonies and spreading.

In a statement, Dr Maria Katsikogianni, Assistant Professor in Biomaterials Chemistry at Bradford University, said: "We are examining patterns with self-cleaning properties found in nature. One of these is found on butterfly wings, which have a tight build-up of cells that resemble ladders close together.

“These not only produce the vibrant colour patterns…but the ladder structure also prevents water from weighing down their wings. More interestingly, the structure makes it difficult for bacteria to fit themselves on top of the wings surface and produce communities.”

Dr Katsikogianni said the team had examined several different anti-bacterial surfaces, including a gecko skin pattern, but the microscopic designs found on butterfly wings is simpler to replicate and should last longer.

She said: “Other natural self-cleaning surface patterns were tried, like gecko skin, however, gecko skin is not a long-lasting solution as the pattern wears down just like it does on the gecko which is why it sheds every so often”.

“If we were trying to replicate something like the gecko skin pattern in the lab, it would be challenging to do this with polymers. It would be quite fragile, and it wouldn't last long enough. So, we started thinking more about patterns with a low aspect ratio. That's when I came across the butterfly wings surface pattern.”

Scientists are now in the process of testing whether the butterfly ‘ladder’ design can be replicated onto surfaces for orthopaedic applications, and to get closer to knowing whether the design affects bone cell attachment and integration with the human body, with no bacteria build up.

Professor Ben Whiteside, director of Centre for Polymer Micro and Nano Technology at Bradford University, works with Dr Katsikogianni to create manufacturing methods to apply the functional surfaces to real-world products.

Working with Professor Stefan Dimov at Birmingham University, the group has developed a route for incorporating the butterfly wing patterns into mould inserts, using laser-based modules for functional surface structuring and texturing.

This allows the mould insert patterns to be replicated on polymeric components by Professor Whiteside, using injection moulding at Bradford University, towards the creation of medical devices, surgical implants or even a range of consumer goods, delivering the added functionalities without requiring coatings or chemicals that could add cost and reduce recycling options.

Professor Whiteside said trials with the plastic patterns showed they can successfully reduce bacterial build up on surfaces while still allowing the growth of tissue cells.

He said: “Technologies in laser patterning, digital manufacturing processes and microscopy have reached a point where we are now able to take a nano-scale 3D pattern measured from a natural surface and apply it directly to man-made objects, which is really exciting.

“These nature-inspired cues open paths for improving performance and minimising infection, while reducing costs, plastic waste and the environmental impact of both medical devices and consumer products.”

Prof Whiteside said the technology could have much wider application, such as antimicrobial, self-cleaning, anti-scratch, anti-squeak and aesthetic surfaces for use in the automotive industry, cosmetic packaging and orthodontics.