Study of Micro/Nano Structure Effects on Hydrophobic Surfaces With High Transparency

This work studies the influences of surface structure on hydrophobicity, and the transmittance of each structure was also taken into account. We investigated three kinds of structures in this work, namely surfaces with nanometer scale, micrometer scale, and hierarchical structures (composed of micro- and nanostructure). The nanostructures and the hierarchical structures on glass surfaces were developed by assembled polystyrene nanospheres; the microstructures on PDMS substrates with different feature sizes were fabricated by soft lithography method. To create a surface with micrometer scale, circular pillars were chosen as the patterns by changing interpillar distance and the height of micropillars. Our results show that as the surface roughness enhanced, the formation of air package between liquid and solid interface contributes to better hydrophobicity. After the surface roughness is enhanced, the surface hydrophobicity increased, whereas the transmittance decreased. A superhydrophobic and nearly transparent surface is obtained on microstructured PDMS surface with water contact angle 153? and transmittance about 90%.Acknowledgement.....................................................................................I bstract...................................................................................................III omenclature...........................................................................................V able of Content.....................................................................................VI ist of Tables........................................................................................VIII ist of Figures.........................................................................................IX haper 1 Introduction 1.1 Motivation 1.2 Literature review 2.2.1 Lotus-effect 2.2.2 Biomimetic technology for superhydrophobic surfaces 4.2.3 Preparation of superhydrophobic surfaces 6.3 Aims and missions 11haper 2 Theory 21.1 Surface energy 21.2 Static contact angle 22.2.1 Young’s equation 23.2.2 Wenzel’s equation 24.2.3 Cassie-Baxter regime 25.3 Contact angle hysteresis 26.4 Wetting transition of water droplets 28haper 1 Introduction 1.1 Motivation 1.2 Literature review 2.2.1 Lotus-effect 2.2.2 Biomimetic technology for superhydrophobic surfaces 4.2.3 Preparation of superhydrophobic surfaces 6.3 Aims and missions 11haper 2 Theory 21.1 Surface energy 21.2 Static contact angle 22.2.1 Young’s equation 23.2.2 Wenzel’s equation 24.2.3 Cassie-Baxter regime 25.3 Contact angle hysteresis 26.4 Wetting transition of water droplets 28haper 3 Experiments and principles of testing equipments 37.1 Materials and reagents 37.2 Preparation of Self-assembled polystyrene crystal films 37.3 Fabrication of microstructured PDMS templates 38.3.1 Fabrication of positive mold by MEMS process 39.3.2 Fabrication of the PDMS microstructured molds and films 41.4 Preparation of PS hierarchical structure 42.5 Soft-lithographic Imprinting 43.6 Measuring Principles of Testing Instruments 44.6.1 Electron microscopy (EM) 46.6.2 Contact angle system 49.6.3 Ultraviolet/visible spectrophotometer (UV/Vis) 50haper 4 Results and Discussion 63.1 Self-assembled polystyrene crystal films 63.2 Master design 65.3 Hierarchical structures 68.4 Soft-lithographic imprinting 70.5 Highly transparent microstructured PDMS films 72haper 5 Conclusions 111eferences..................................11