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Laser texturing for 'self-cleaning'

Water scarcity is emerging as a major environmental problem in the 21st century, fresh water is an essential ingredient for life and scarcity will have global repercussions.

The reduction of water usage and minimisation of waste is essential for sustainable industrial practice. One approach to improve water usage involves the use of superhydrophobic surfaces which remove dirt and debris through a ‘self-cleaning mechanism’, in this approach water droplets roll freely on the surface picking up and removing dirt particles.

Recent studies investigating the use of superhydrophobic surfaces have shown better cleaning of dust from solar panels in the desert using small amounts of water (1), reduced bio fouling for seafaring ship hulls (2) and the avoidance of bacterial adhesion to stainless steel in the dairy industry (3).

The focus of this PhD project is the fabrication of superhydrophobic surfaces through direct laser texturing of metals. This process imparts superhydrophobicity through inherent modification of the surface texture and chemistry without the use of coatings. The laser texturing process has proven capable of producing some of the most strongly nonwetting surfaces ever created with key benefits of low cost, scalability and HSE neutrality. My approach is to use nanosecond pulsed fibre lasers which allow for a much faster areal processing rate than has been reported in the literature. A recent development has involved testing the use of heat treatment to accelerate the post-laser chemical decomposition process, reducing for the superhydrophobic property to develop from a month to a day.

 

A water droplet rests on a rough hydrophobic surface


There are many questions still to answer about the exact type of surface structure best suited to the functionality, how durable we can make superhydrophobic surfaces, and the exact reaction pathway underlying the chemical transition of the surface after laser processing. Because of the potential benefit produced by surfaces which reduce water usage for cleaning, these fundamentals should be researched keenly and with open discussion to progress the technology.

 

James MacDonald

NanoDTC PhD Associate 2017

References

1.            Yilbas BS, Hassan G, Al-Sharafi A, Ali H, Al-Aqeeli N, Al-Sarkhi A. Water Droplet Dynamics on a Hydrophobic Surface in Relation to the Self-Cleaning of Environmental Dust. Scientific Reports. 2018 Feb 14;8(1):2984.

2.            Zhang H, Lamb R, Lewis J. Engineering nanoscale roughness on hydrophobic surface—preliminary assessment of fouling behaviour. Sci Technol Adv Mater. 2005 May;6(3–4):236.

3.            Lutey AHA, Gemini L, Romoli L, Lazzini G, Fuso F, Faucon M, et al. Towards Laser-Textured Antibacterial Surfaces. Scientific Reports. 2018 Jul 4;8(1):10112.

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