Role of nanoscale topography on the hydrophobicity: A study of fluoro-based polymer film on silicon and carbon nanotubes

The unique electronic, mechanical and chemical properties of carbon nanotubes making them most promising candidate for the building blocks of molecular-scale machines, and nanoelectronic devices. On the other hand, highly hydrophobic films are being actively considered in silicon based micro-electromechanical systems, nanotechnology based devices, optoelctronic devices, or biomedical devices to reduce adhesion that may be encountered during wet processing. In order to fill the gap, and fulfil the requirements, it could be proved that morphological changes in the nanometer range influences the water contact angles and their hystersis of low-surface energy materials. Thin films of fluorine based block copolymer itself forms nano-hemispheres (similar to lotus leaf) at and above 100°C favoring an increase in the water contact angle from 122° (25°C) to 138° (400°C). The structural, optical, mechanical and hydrophobic properties of fluorine based block co-polymer are also discussed. By applying nanolayered (5 nm) fluorine-based block co-polymer film on a aligned carbon nanotubes (CNT) morphology with a certain roughness, the advancing contact angle for water on fluoro-based polymer film on a nearly atomically flat Si wafer increased from 122° to 138° (close to super hydrophobicity) and 150° on the rough asparagus-like structure of CNT has been observed.