The role of nanoscale topography on super-hydrophobicity: A study of fluoro-based polymer film on vertical carbon nanotubes

Abstract

The unique electronic, mechanical and chemical properties of carbon nanotubes make them most promising candidates 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, optoelectronic devices, or biomedical devices to reduce adhesion that may be encountered during wet processing. In order to fill the gap, and fulfill the requirements, it could be proved that morphological changes in the nanometer range influences the water contact angles and their hysteresis of low-surface energy materials. Thin films of fluorine based block co-polymer 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 vertically 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.