Nano- and microstructures can now be incorporated into surfaces in the blink of an eye using lasers. The technology is being developed and marketed by the young Dresden-based company Fusion Bionic - a spin-off of the Fraunhofer Institute for Material and Beam Technology IWS. There are no limits to the imagination when it comes to laser structuring. Its advantage: it is fast and much more versatile than coatings.
Laser lotus effects
Modern light interference technologies from Dresden make it possible to quickly transfer other sophisticated structural tricks of nature to technical surfaces such as battery components, implants or aircraft Product surfaces can be enhanced with many different effects. With the lotus effect, for example, a microstructure ensures that dirt does not adhere, but is simply washed off the next time it rains. The fine ripples of sharkskin, on the other hand, improve the airflow on the outside of airplanes and ships, which saves fuel. Until now, many of these nature-inspired effects have been created by coating the surface or applying films with microstructures embossed into them. However, coatings and films can wear off, so that the desired effect diminishes over time. In recent years, researchers at the Fraunhofer IWS and the Technical University of Dresden have brought an alternative method to market maturity with which surfaces can be permanently provided with nano- and microstructures: Direct Laser Interference Patterning (DLIP). In this process, the nano- or microstructure is inscribed directly into the surface by laser to create biomimetic effects. The high speed of the process, which can currently process an area of up to one square meter per minute, is remarkable. The new technology is so promising that the company Fusion Bionic was spun off from the Fraunhofer IWS this year. Fusion Bionic develops and sells DLIP system solutions for biomimetic surface finishing, but also carries out surface functionalization itself on behalf of customers.
Fast enough for large surfaces
"Compared to coating or bonding, lasers were long considered far too slow to finish large surfaces," says Fusion Bionic Managing Director Dr. Tim Kunze, who founded the company together with three partners. "With the DLIP process, however, we have made the step towards fast processing of large surfaces." Traditionally, a laser beam is thought of as a single fine beam. If you wanted to use it to carve a pattern into a surface like a needle, you would lose far too much time. The DLIP process works differently. First, a laser beam is split into several beams. In order to create a pattern on the surface, the many laser beams are superimposed in a controlled manner to create what is known as an interference pattern. This pattern can be distributed over a larger area, which makes large-scale and fast processing possible.
The principle of interference is quickly explained: light spreads out in waves. If two light beams are superimposed, their wave troughs and peaks can cancel each other out or intensify each other. Where light hits the surface, material is removed or changed by the laser energy. The dark areas remain untouched. "We can create almost any structure imaginable," says Tim Kunze. "Lotus effect, sharkskin, moth eye and much more."
Laser processes can also create biocompatibility or antibacterial properties in hip prostheses, for example
While he was still at the Fraunhofer IWS, his team worked closely with Prof. Andrés Lasagni from the Technical University of Dresden and Airbus to develop a microstructure that prevents ice from accumulating on the wings during flight. In conventional jets, this is prevented by directing warm exhaust air from the engines into the wings. However, this causes the engines to lose energy. The project has shown that the energy requirement of an ice protection system is reduced by 80 % if the wing also has a DLIP microstructure. "This would also be a solution for future electrically powered aircraft in particular, as no waste heat from the engines would be available," says Tim Kunze. In other projects, implants such as hip joint prostheses and dental implants have been processed so that their surfaces are particularly biocompatible or have an antibacterial effect.
Funding through the Fraunhofer Ahead program
If the wing of an airplane has a microstructure applied by laser, the wing's ice protection system saves around 80 % energy The impetus for the development of DLIP came a good ten years ago when laser expert Prof. Andrés Fabián Lasagni moved from the University of Saarbrücken to the Fraunhofer IWS and focused on the technology. At the time, DLIP was more of an academic basic topic. However, Lasagni, who now holds the professorship for laser structuring of large surfaces at the TU Dresden, realized that it had great potential. He built up a powerful team at the Fraunhofer IWS, which continued to grow under his successor Tim Kunze from 2017. Building on Lasagni's pioneering preliminary work, the two worked together to develop industrial-grade DLIP optics, which have since been installed at numerous pilot customers worldwide. In 2020, it became clear that the commercialization of DLIP technology needed to be taken to a new level. "Our solutions offer a completely new degree of freedom in surface design at an unprecedented speed, enabling new types of products and processes," explains Tim Kunze.
Fusion Bionic has now been founded with funding from the Ahead program, with which the Fraunhofer-Gesellschaft enables spin-offs. "There is a great need for the functionalization of surfaces," Lasagni sums up. "Every industry has its own challenges, be it the adhesion of ice cream to container walls or the reduction of friction. In this respect, we won't run out of work any time soon."
In order to accelerate the development of innovative surfaces, Fusion Bionic is working on a prediction platform based on artificial intelligence with the support of its investor Avantgarde Labs Ventures. This will be used to realize advanced laser functionalities. In parallel, an "AI Test Bench" is being set up at the Fraunhofer IWS, a multi-sensor test bench for laser processing on which the optimal surface structure for each problem can be quickly predicted and generated with the help of artificial intelligence.
Video: Superhydrophobic surfaces:
