Superhydrophobic surface textures generated by Ultra Short Laser Pulses for anti-ice applications in aviation
Research group: prof.dr. ir. A.J. Huis in' t Veld, dr.ir. G.B.R.E. Romer, MSc D. Arnaldo del Cerro (contact person)
Project term: February 2009 till February 2013
CleanSky is a European funded project aiming at a radical reduction of noise and emissions in air transport and aircraft fuel consumption. CleanSky is built upon six different technical areas (known as Joint Technology Initiatives (JTIs), see http://www.cleansky.eu
Figure 1: Cleansky Joint Technology Initiatives.
The Chair of Applied Laser Technology is involved in the CleanSky Work Package on Surface Technologies. One of the research topics in this Work Package is the design of Anti-Icing-surfaces, consisting of understanding chemistry and physics, development of materials and processes, validation of function, lifetime prediction, development of model coatings and preparation of coatings and active systems for ground- and flight demonstration.
Laser surface texturing techniques has been successfully developed on micro-meter and nano-meter scale, which makes surfaces super hydrophobic. This technique has also proved to reduce ice accumulation under icing rain conditions.
By laser ablation with ultra-short laser pulses in the pico- and femto-second range, well controlled superimposed micro- and nano-scaled surface textures can be obtained. The microscale of the texture is mainly determined by the dimensions of the laser spot, whereas the superimposed nano-structure is the result of so-called laser induced self-organizing nanostructuring. By controlling this dual micro-nano surface texture, it is possible to modify the natural hydrophobicity of materials, see figure 2.
Figure 2: Two water drops on stainless steel. The left drop sits on top of a micro structured surface exhibiting a high contact angle; the surface on the right is smooth and wets the surface.
Leading edges, engine inlets etc. of airplanes are prone to ice-accretion under certain icing conditions. An ice layer disturbs the air flow over the wing and reduces the aircraft aerodynamic performance, sometimes with fatal consequences.
Status of the project
Popular materials in aviation have been laser-machined and its surface texture has been analysed using AFM, SEM and confocal microscopy. Hydrophobic coatings have been applied on top of the textures by PE-CVD, in order to create superhydrophobicity. The water repellent properties of the surfaces have been quantified by contact angle measurements, and its anti-ice properties have been studied in a climate chamber.
Wetting and ice accretion analyses are being performed to design and optimize an ice-phobic surface texture, considering the manufacturing process constraints and the durability requirements.