Bionics: Textured non-stick coatings inspired by nature
In the last ten years, the term bionics, an artificial word from biology and technology, also known as "technical biology" or biomimetics, has grown in importance.
After the beginnings in Germany at the University of Saarland, Saarbrücken, the two most popular examples from basic research are the Riblet film, developed at the University of Saarbrücken using the example of the skin of sharks, and the Lotus effect, discovered and put into industrial use by the University of Bonn after the model of the leaf top of the lotus plant. Both developments are based on the initially astounding discovery that nature prefers finest-textured surfaces if engineers use as smooth as possible.
The company Rhenotherm Kunststoffbeschichtungs GmbH has been specializing in fluoropolymer-based industrial coatings for the application areas of non-stick, dry lubrication and corrosion protection for 30 years and is open to continuous development of coating systems to serve varying customer requirements. Some developments have been patented, including Lotuflon®, a microstructured fluoropolymer coating with different structural levels.
Rhenotherm is involved in a BMBF-funded joint project (support VDI, FKZ 13N8676) for the development of novel and durable anti-adhesive coatings.
Both in terms of optimum flow around air or water and on the lowest adhesion of particles, microstructured surfaces
Smooth surface smooth because the boundary layer of the flow is positively influenced. This avoids stifling turbulence while reducing pollution, which is not only a matter of aesthetics, as it results in increased weight and reduced streamline shape and is vital to organisms by reducing pathogen infestation. In technical developments, such as the construction of aircraft and ships, this aspect of anti-fouling is becoming increasingly important, especially because of the currently enormous increase in fuel and transport costs.
Biological structures are usually optimized with regard to several problems and are often built up with larger structural molecules and their ability to self-organize, which often requires structuring. Going beyond self-cleaning in connection with water, the anti-adhesion property of a microstructured surface is of increasing industrial importance: as described using the example of the lotus effect, different sizes (hierarchies) of the leaf surface such as leaf veins, epidermal cells and wax crystals in their combination reduce the contact area by up to 96%. Such structures, derived from the biological models, are used in the Plasma Coatings® systems from Rhenotherm Kunststoffbeschichtung GmbH. Starting from structured basic structures that are built up on the base body, these are coated with various non-stick materials. The basic structure is applied by sandblasting using thermal spraying or plasma coating. Either hard metals or ceramics (aluminum oxide, tungsten carbide, etc.) are used for this.
About the basic structure thus constructed you bring the appropriate anti-adhesive layer. This may consist of fluoropolymers (Teflon ™) or silicone. The field of application of these Plasma-Coatings® coatings is manifold: In the adhesives industry, deflection rollers for adhesive tapes, diapers, labels, etc. have been coated.
In the printing industry, rolls are coated for the lamination process. In the field of converting such coatings are increasingly used. The coating is not only non-sticky, but also has traction due to its structure, which can be beneficial in many cases. Depending on the non-stick material, the surfaces are absolutely chemically resistant, but also electrically conductive to electrostatic charges
to prevent. Even in elastomer production and in the rubber industry, these types of coating are used.
In contrast to these structured coatings, Rhenotherm Kunststoffcoatings GmbH is also able to produce super-smooth non-stick coatings based on PTFE and PFA. Super-smooth surfaces (Ra < 1 µm) are achieved with multiple layers and various polishing processes. The layer thickness can be manufactured with a tolerance of 5 µm, whereby excellent concentricity can be achieved.