A group of scientists from Europe has harnessed new photonics technology to develop superhydrophobic, antibacterial metal surfaces, taking us a step closer to self-cleaning saucepans, toilets, and dishwashers.
Surface of a lotus leaf. Image credit: William Thielicke / CC BY-SA 4.0.
Taking their ideas from defense mechanisms found in plants such as lotus (genus Nelumbo), the researchers have made a breakthrough that will enable the production of self-cleaning sheet metal on an industrial scale.
The new technique, developed in the TresClean (High Throughput Laser Texturing of Self-Cleaning and Antibacterial Surfaces) project, will initially be used to create antibacterial surfaces for use in the food production industry – dramatically increasing productivity and reducing costs in factories which process biological food products such as milk, tomato sauce, and yoghurt.
The scientists have used high-power laser cutting devices to create a specifically tailored, rough micro-topography on sheet metal that mimics the surface of the lotus leaf, causing liquids to ‘bounce off.’ This roughened surface creates miniature pockets of air that minimizes the contact area between the surface and a liquid.
“In the same way that lotus leaves keep themselves clean, without the need for cleaning products or chemicals, their jagged, rough surfaces enable water to stay as spherical droplets by preventing spreading,” said Prof. Luca Romoli from the University of Parma in Italy, coordinator of the TresClean project.
“Bacteria do not get a chance to stick because the contact with the metal surface and the liquid is reduced by over 80%. We are looking at an anti-bacterial metal.”
While this replicating approach may currently exist for specific and expensive plastic components, it is a first for self-cleaning metal.
Metal surfaces are textured using innovative industrial photonics devices: high-average power ultrashort-pulsed lasers are used in combination with high-performance scanning heads by utilizing an innovative beam delivery method enabling movements of up to 200 m/s.
The project team can achieve this surface texturation quickly by cutting areas of 500 cm2 in less than 30 min.
In early 2015 production methods could make laser-etched metal at a rate of 6.45 cm2/hr, whereas TresClean can produce 1,000 cm2 in the same period of time, making this technology 155 times quicker than before.
“Vats in milk factories need to be cleaned every 6-8 hrs to avoid the exponential growth of bacteria. This hinders usage and therefore affects output,” Prof. Romoli said.
“By saving hours per day in cleaning, it will yield an efficiency improvement stemming from fewer sterilization cycles and less cleaning time within production as a whole. This will also reduce energy consumption as a result of fewer cleaning phases making food production quicker, safer and more profitable”.
“It is possible that any use of metal that needs to avoid the formation of bacteria will benefit from the TresClean product, such as medical cutting tools, sterile surfaces, dishwashers, or even saucepans,” Prof. Romoli added.
