Injection Molding of Superhydrophobic Liquid Silicone Rubber Surfaces

Abstract

Superhydrophobic functional surfaces have numerous applications. Their self-cleaning ability and the associated savings in energy, water and cleaning agents enhance the sustainability of products and often make active cleaning of these surfaces unnecessary. Silicone surfaces, which aim to imitate the surface of the lotus plant, were prepared using a microstructured injection mold. The conical micro structures were varied in diameter and height ranging from 5 to 20 $\upmu$m as were the process parameters within the framework of a statistical experimental plan. The molded structures were evaluated by scanning electron microscopy and confocal laser microscopy, and the resulting contact angle was measured. In contrast to the structural dimensions, the process parameters had only a minor impact on the contact angle. Smaller base diameters of the individual cones and the resulting smaller distances between the cone tips produced larger contact angles. Larger aspect ratios and increasing heights at equal intervals of the individual structures led to smaller standard deviations from the mean measured contact angles. Subsequent mechanical load tests showed the resistance of the functionalization. Our results reveal that it is possible to produce robust superhydrophobic surfaces in a single-step liquid silicone injection molding process.