Design, fabrication and characterization of three-dimensional patterned microstructured surfaces with self-cleaning properties from hydrophilic materials

The generation of self-cleaning surfaces requires strong water repellence, which is usually realized by either fabricating a rough surface from low-surface-energy material, or modifying a rough surface with microstructures. The advancement of the ultra-precision machining technology enables the later approach to be a more prospective and flexible method to produce microstructured self-cleaning surfaces. This article presents a study for the design, fabrication and characterization of three-dimensional patterned microstructured surfaces with self-cleaning properties by using ultra-precision machining technology. The study starts with the design of three-dimensional microstructured surfaces based on the derivation and simplification of some microstructures possessing self-cleaning properties in nature, and theoretical analysis for water contact angle of the designed structures. According to the scales and patterns of the three-dimensional microstructures, an appropriate ultra-precision machining method is selected to fabricate the microstructures. The machined surface is then examined and characterized. A series of experiments have been undertaken to produce patterned microstructures by an ultra-precision raster milling process, and the micro-structured surfaces were measured and characterized in terms of their geometrical form accuracy and water repellence performance. The experimental results indicate that such kind of three-dimensional patterned microstructures can achieve a large static water contact angle, which is near 150°, by modifying the structural scales and patterns of hydrophilic materials. This provides an important means to generate surfaces with self-cleaning properties in mass production by precision injection moulding.