TresClean Project Achieves Major Goal
The TresClean project has recently achieved a major goal in successfully demonstrating ultrashort pulsed laser-textured antibacterial surfaces. After carefully designing ideal surfaces for reduced bacterial attachment, consortium members used ultrashort laser pulses with a duration less than 350 fs (0.00000000000035 s!) to produce extremely fine features on stainless steel surfaces. Laserinduced period surface structures (LIPSS), or elongated ridges with a separation distance of about 0.0007 mm, and laser-induced nano-pillars (LINP), or microscopic spikes separated by about 0.001 mm, were both created over areas
of 250 mm2 . Textured samples were then immersed in solutions containing Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria for two hours, after which the number of residual bacteria on each surface was determined. Lasertextured samples were found to achieve reductions of up to 99.8 % in E. coli retention and 84.7% in S. aureus retention compared to control samples, which had been chosen to reflect current industry practises for food handling and packaging equipment. These results represent vast improvements over standard stainless steel surfaces and have huge implications for the future of food handling and other industries in which biofouling and bacterial contamination are problems, including domestic appliances and healthcare.
To achieve the above-mentioned outcomes, the TresClean consortium focused on two key characteristics of laser-textured surfaces: topography, or form, and wettability, or the tendency of water to either spread out or detach from a surface. The aim was to produce surfaces that did not allow bacterial retention by taking inspiration from the “bed of nails”. From a distance, the bed of nails behaves as a homogeneous surface on which the “fakir” can lie without injury; however, to objects similar in size to the nails, the surface is an extremely hostile environment. The project team was able to produce LIPSS and LINP with characteristic surface features smaller than E. coli cells and similar in size to S. aureus cells, thus reducing the number of available contact points and limiting how well bacterial cells could remain attached to the surface. Laser-textured surfaces were also hydrophobic, or water-repellent, which was found to be important in limiting retention of certain bacteria types.
The project will now focus on upscaling of laser technology based on results obtained so far to achieve industrially relevant texturing rates and throughput. This will include testing a newlyacquired 350 W average power ultrashort pulsed laser source and development of a 1 kW average power ultrashort pulsed laser source, high-efficiency frequency conversion chains and high-speed scanning optics. Upscaling is expected to be completed by mid-2019, following which a productivity demonstrator will be produced to show the full potential of ultrashort pulsed laser processing as an industrial technology for producing antibacterial surfaces.
TresClean has been granted 3.3m € in funding from the European Union’s H2020 ICT 2015 (Grant Agreement No. 687613) and sees involvement of the Università degli Studi di Parma, Universitaet Stuttgart, Centre Technologique ALPhANOV, Raylase AG, Ecor Research SPA, BSH Electodomesticos Espana SA and Modus Research and Innovation Ltd. Results obtained to date can be found in an article published in Scientific Reports by consortium members: https://www.nature.com/articles/s41598-018-28454-2. For further details and to follow the work progress, please visit TresClean’s website on www.tresclean.eu.