Optimization Modeling of Biomimetic Structures for Self-Cleaning and Optical Performance in Ultra-precision Raster Milling

An optimization model of biomimetic structures with self-cleaning properties and optical performance was successfully established by defining constrains of static contact angle and transmittance based on the geometrical parameters of the designed patterns in mathematical approach. A balance can be stricken between the wetting and optical performance. After the establishment of the optimization model, experimental validation was conducted to evaluate both the wetting and optical performances of the micro-grooves and the micro-pillars fabricated by ultra-precision raster milling. The experimental results show that surface geometry is one of the major factors which govern the static contact angle. A critical range of wetting performance can be identified according to the fabricated samples with different surface geometrical parameters of micro-grooves. On the other hand, the experimental results indicate that the optical performance of the designed biomimetic structures in term of transmittance can be controlled in ultra-precision raster milling. It was found that all the optical images displayed from the micro-grooves and micro-pillars on the COC samples were clear, with or without light reflection, by controlling the roughness of the flat areas at the top and the bottom surfaces of the micro-patterns using a faceted single-crystal diamond cutting tool. Structural parameters for self-cleaning properties have been identified and provide an important guide for the development of advanced self-cleaning surfaces.