Laser process etches anti-fouling hull surface

Paints and varnishes are used as ship coatings to stop algae or drag-enhancing barnacles sticking to hulls, but these can be harmful to the environment.

Now, European scientists are developing a 1kW, ‘dot matrix’ ultrafast laser system that can carve flow-optimised metal or plastic surfaces.

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Etching tiny ‘spike’ structures onto sheet metal or plastic, the new laser system can reportedly create a rough surface at a microscopic level. This uneven topography can reduce drag or inhibit the growth of bacteria, algae or even barnacles.

The idea for this maritime application has been inspired by shark’s skin, which is covered in millions of microscopic denticles - or tiny protruding scales – that reduce drag to make it a highly efficient swimmer. Similarly, engraved metal or plastic surfaces can have 'anti-fouling' properties that prevent contaminants or microorganisms from adhering to them.

Funded by the Photonics PPP, the scientists behind the €4.7m laser project hope that specially-designed structures on steel ship hulls might help to reduce fuel consumption and replace harmful coatings.

In a statement, Dr Johannes Finger, coordinator of the MultiFlex project, said: “Laser-fabricated surface structures have the potential to reduce friction and to prevent the growth of plants and algae. This could significantly reduce ship repair, maintenance, CO2 emissions and fuel bills while providing an alternative to harmful coatings that are toxic to the environment.”

“Besides maritime components, application fields can be found in aircraft and turbomachinery. Here, surface structures might inhibit cavitation and thus improve lifetimes of propellers of propulsion systems or water turbines.

“Our photonics system can also create design textures or ‘microcavities’. Here the environment benefits by replacing environmental problematic technologies like chemical etching.”

In the same way that dot matrix printers use a moving head, printing in a line by line motion, the laser sends super-fast pulses of concentrated energy to ablate materials that are difficult to work with. The system splits a single beam into a grid of 64 ‘beamlets’, where each ray can be turned on, off, positioned, and individually ‘tuned’.

“Existing ultrafast lasers are known for their precise ablation and cutting results. Unfortunately, processing large parts with such lasers can take weeks. Our system will ablate more than 150mm³ in one minute,” said Dr Finger.