Transparent ultra-hydrophobic surfaces

• Published in: Journal of adhesion science and technology Vol. 21; no. 5-6; pp. 399 - 408
• Main Authors: Rios, P. F., Dodiuk, H., Kenig, S., McCarthy, S., Dotan, A.
• Format: Journal Article
• Language: English
• Published: Leiden Taylor & Francis Group 2007; Brill
• Subjects: Applied sciences; COATINGS; Composites; CONTACT ANGLE; Exact sciences and technology; Forms of application and semi-finished materials; HYDROPHOBIC SURFACES; INTERFACIAL ADHESION STRENGTH; LOTUS EFFECT; NANOROUGHNESS; Polymer industry, paints, wood; POSS; SLIDING ANGLE; Technology of polymers; Nanoroughness; Coating material; Silsesquioxane polymer; sliding angle; Roughness; contact angle; interfacial adhesion strength; Hydrophobicity; Lotus effect; Experimental study; Functional polymer; Silica; Composite material; Wettability; coatings; Polyhedral molecule; Morphology; Concentration effect; hydrophobic surfaces; Surface properties; POSS; Transparent material
• ISSN: 0169-4243; 1568-5616
• DOI: 10.1163/156856107780474975

Self-cleaning surfaces have received a great deal of attention, both in research studies and commercial applications. Both transparent and non-transparent self-cleaning surfaces are highly desired, as they offer many advantages and their potential applications are endless. As in many other cases, also in the case of self-cleaning surfaces, nature found a solution before man. The Lotus flower is a symbol of purity in Asian cultures, even when rising from muddy waters it stays clean and untouched by dirt, organisms and pollutants. The Lotus leaf "self-cleaning" surface is hydrophobic and rough, showing a two-layer morphology. While hydrophobicity produces a high contact angle, the two-layer morphology reduces the adhesion of dirt and water drops to the surface. Because of this low adhesion, water drops easily slide across the leaf surface carrying the dirt particles with them. In the present work the Lotus leaf morphology was mimicked using hydrophobic chemistry and a two-layer topography, with a base layer of silica and a top layer of intrinsically nanostructured polyhedral oligomeric silsesquioxanes (POSS) particles. Results have indicated that, thus, a transparent ultra-hydrophobic coating can be obtained. When these materials were mixed and used as a single layer the hydrophobicity deceased significantly. The contact angle and sliding angle measurements were supported by AFM micrographs.