Superhydrophobic surfaces have attracted a lot of attention since the potential applications of self-cleaning effect in self-cleaning textiles, fluid transport in micro/nanofluidics, bio-MEMS and so on. Different techniques have been developed to fabricate superhydrophobic surfaces with roughness in micro or nano scale. However, the surfaces with submicron scale and the corresponding geometric effects on superhydrophobicity have never been investigated in detail. Another type of superhydrophobic surfaces frequently reported in recent years are dual-scaled lotus-leaf-like surfaces. However, existing fabrication techniques always involve expensive and complicated procedures. In this thesis, cylindrical pillar array surfaces with diameter ranging from few hundreds microns to submicron and...[ Read more ]

Superhydrophobic surfaces have attracted a lot of attention since the potential applications of self-cleaning effect in self-cleaning textiles, fluid transport in micro/nanofluidics, bio-MEMS and so on. Different techniques have been developed to fabricate superhydrophobic surfaces with roughness in micro or nano scale. However, the surfaces with submicron scale and the corresponding geometric effects on superhydrophobicity have never been investigated in detail. Another type of superhydrophobic surfaces frequently reported in recent years are dual-scaled lotus-leaf-like surfaces. However, existing fabrication techniques always involve expensive and complicated procedures. In this thesis, cylindrical pillar array surfaces with diameter ranging from few hundreds microns to submicron and different heights have been fabricated by combination of improved photolithography, plasma ashing technology and meticulously adjusted deep reactive iron etching (DRIE). The apparent contact angle (ACA) study shows that the solid fraction, the diameter, the spacing between pillars and the height of pillars will influence the superhydrophobic property.

On the other hand, a low cost and efficient approach to mimic lotus-leaf like surface has been developed by 1-mask photolithography, DRIE and Carbon nanotube (CNT) Microwave Plasma Enhanced CVD (MPCVD). As a result, novel Nanostructured micro Flowers (nano-flower) were fabricated. The ACA testing shows it was increased dramatically compared to silicon (~140%) and parylene-coated (~78%) micropillar surfaces with the additional petal-like CNT structure. The sliding angle and dynamic testing indicate that these nano-flower surfaces are stable superhydrophobic surfaces. Both theoretical analysis and growth process experiments demonstrated that the growth mechanism of nano-flower was dominated by the special electric field distribution and the stress in CNT cluster. Finally, the wetting dynamic testing shows the petal-like structures have special function on superhydrophobicity.