Fabrication of Bioinspired Micro/Nano-Textured Surfaces Through Scalable Roll Coating Manufacturing

Bio-inspired, micro/nanotextured surfaces have a variety of applications including superhydrophobicity, self-cleaning, anti-icing, antibiofouling, and drag reduction. In this paper, a template-free and scalable roll coating process is studied for fabrication of micro/nanoscale topographies surfaces. These micro/nanoscale structures are generated with viscoelastic polymer nanocomposites and derived by controlling ribbing instabilities in forward roll coating. The relationship between process conditions and surface topography is studied in terms of shear rate, capillary number, and surface roughness parameters (e.g., Wenzel factor and the density of peaks). For a given shear rate, the sample roughness increased with a higher capillary number until a threshold point. Similarly, for a given capillary number, the roughness increased up to a threshold range associated with shear rate. A peak density coefficient (PDC) model is proposed to relate capillary number and shear rate to surface roughness. The optimum range of the shear rate and the capillary number was found to be 40-60 s(-1) and 4.5 x 10(5)-6 x 10(5), respectively. This resulted in a maximum Wenzel roughness factor of 1.91, a peak density of 3.94 x 10(4) (1/mm(2)), and a water contact angle (WCA) of 128 deg.