The fine ripples of shark skin, meanwhile, improve the dynamics of air and water on the outside of airplanes and ships, thus saving fuel. With nature as their inspiration, many such effects have been developed by coating or applying a film to the surface into which the microstructures are incorporated. Coatings and films can wear away, however, causing the desired effect to diminish over time. In recent years, researchers at Fraunhofer IWS and Technische Universität Dresden have developed an alternative, market-ready method of permanently applying nano- and microstructures to surfaces: Direct Laser Interference Patterning (DLIP). This process incorporates the nano- or microstructure directly into the surface using a laser in order to create biomimetic effects. It is a remarkably quick process, and can currently handle up to one square meter of surface per minute. The new technology is so promising that it led to Fusion Bionic being founded this year as a spin-off from Fraunhofer IWS. Fusion Bionic develops and markets DLIP system solutions for biomimetic surface finishing, but also provides surface functionalization services to its customers.
"For a long time, lasers were much too slow to be used for finishing surfaces with large areas compared to coating or applying films," says Managing Director of Fusion Bionic, Dr. Tim Kunze, who founded the company together with three partners. "But with the DLIP process we've made the leap to processing large surface areas quickly." Conventionally, people think of a laser as a single fine beam. Using it like a needle to make a pattern in a surface would be extremely time-consuming. The way the DLIP process works is different. First of all, it splits a single laser beam into multiple clusters of beams. To apply a pattern to the surface, these multiple laser beams are superimposed in a controlled way to create what is known as an interference pattern. This pattern can be distributed over a wider area, allowing surfaces with large areas to be processed rapidly.
Let's briefly explain the principle of interference: Light is transmitted in waves. When two beams of light are superimposed, their wave troughs and crests can cancel each other out or reinforce each other. Where light hits the surface, the laser energy removes or alters part of the material. The dark areas remain unaffected. "This allows us to create virtually any structure imaginable," says Tim Kunze. "Lotus effects, shark skin, moth eyes and many more."
During his time at Fraunhofer IWS, his team worked closely with Prof. Andrés Lasagni of Technische Universität Dresden and with Airbus to develop a microstructure that prevents ice from building up on airplane wings during flight. Traditionally, this is achieved by piping hot exhaust air from the aircraft engines to the wings. However, this wastes energy from the engines. The project found that the energy required by an ice protection system decreased by 80 percent when the wings also incorporate a DLIP microstructure. "This is an especially good solution for the electrically powered planes of the future, because those engines won't generate any waste heat," says Tim Kunze. Other projects have worked on processing implants such as prosthetic hip joints and dental implants to make their surfaces especially biocompatible or antibacterial.
COMPAMED-tradefair.com; Source: Fraunhofer-Gesellschaft
