NEWS FROM AILU
Laser surface textures find applications across industry
Dave MacLellan, executive director of AILU, takes us through some of the topics covered at a recent workshop on laser surface texturing
Laser surface textures are finding applications in several industries. These bio-inspired surfaces can be used for modifying the wettability (making surfaces attract or repel water droplets), the tribology (modifying the performance of a surface regarding friction or wear) or the optical reflectivity (changing colour or contrast) of surfaces. These surfaces can be used in applications as diverse as biomedical, surgical implants, aircraft surfaces, engine and gear train components, white goods and currency or luxury goods. The latest AILU workshop,
which took place at Cranfield University, explored various aspects of this application and the laser technology to support it. As well as providing a forum to exchange ideas in the form of engaging presentations, the workshop was backed up by a range of industrial exhibitors and networking opportunities.
Processing techniques When functional surfaces are applied to components for industrial applications, there is a need to make the rate of laser processing sufficiently rapid to be economical. This can be achieved with a combination of higher powers and faster scanning speeds, or alternatively multiple beamlets that can apply hundreds of small spots in an array simultaneously. At HiLASE, near Prague in the Czech Republic, the latest
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results in this field involve using a diffractive optical element supplied by HoloOr of Israel, together with a Perla 100 picosecond laser built at HiLASE with high pulse energy (20mJ) and high frequency (up to 200kHz repetition rate). Using this method it is possible to reach high speeds of patterning. The goal is to reach speeds higher than 1 square metre per minute. Alternative techniques
use direct laser interference patterning, which sees a combination of laser beams forming an interference pattern
“There is a need to make the rate of laser surface texturing sufficiently rapid to be economical”
to achieve smaller features than the diameter of the beam. This technique can also produce high- speed patterning with the same goal. This technique is offered by Fusion Bionic, a German company based in Dresden that spun out of Fraunhofer IWS. The application of this technology can be based around different laser sources (in terms of wavelength and pulse duration), depending on the material, the application and the geometry required.
Tribology applications At the MTC (Manufacturing Technology Centre) and Loughborough University, work is being carried out on the texturing of cutting tools to change their friction performance. Tools made from synthetic diamond and textured by laser can have reduced coefficient of friction, and the grooves or pockets made by laser processing can act as reservoirs for lubricant, which can also improve tool life and reduce wear. This process can result in longer-lasting cutting faces and reduce the costs and inconvenience of replacing worn tools so frequently.
Wettability in electronics In the field of circuit boards for microelectronics, Watt-Laser has applied laser surface texturing to make hydrophobic surfaces that repel water and oils, making the surface corrosion-free, which can act as a pre-treatment for soldering. This avoids the need for precious metal coatings that already contribute a large cost in the electronics industry.
Optical advances PowerPhotonic is using novel manufacturing techniques to make complex lenses. Microlens arrays (pictured) and homogenisers using designs inspired by nature are produced using laser material processing to ablate the lens material and then polish or re-melt the surfaces to improve the smoothness and optical performance.
Laser sources At Lithuanian firm Light Conversion, femtosecond laser sources are developed that target applications in surface structuring, including high
PowerPhotonic produces microlens arrays featuring bio-inspired surfaces using laser texturing
contrast marking, polishing, ablation and micro-machining. In the case of periodic structures, femtosecond lasers are used in applications such as the preparation of surfaces to reduce transmission losses using a ‘moth eye’ structure to prepare these optical parts. The particular case study presented at the workshop in Cranfield was the processing of Mach-Zehnder Interferometers, where ultrashort laser pulses accurately structure the trenches required to produce these precise tools. A full video of the workshop
on surface texturing is available after the event at the online delegate rate (as are prior online or hybrid workshops). The next AILU workshop will be a meeting at the MTC near Coventry on 29 September, on high-power laser welding, which will explore research and industrial state- of-the-art applications in this area. l
www.ailu.org.uk/events info@ailu.org.uk +44 1235 539595
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PowerPhotonic
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