Bioinspired, micro/nano-textured surfaces have a variety of applications including superhydrophobicity, self-cleaning, anti-icing, anti-biofouling, and drag reduction. In this paper, a template-free and scalable roll coating process is studied for fabrication of micro/nano-scale topographies surfaces. These micro/nano-scale 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. The optimum range of the shear rate and the capillary number was found to be 40-60 s-1 and 4.5×105- 6×105, respectively. This resulted in a maximum Wenzel roughness factor of 1.91, a peak density of 3.94×104 (1/mm2), and a water contact angle (WCA)of 128°.

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Bioinspired Micro/Nano textured rough topography of a surface has many applications in super-hydrophobicity, self-cleaning surface, anti-icing coatings, anti-biofouling, and drag reduction surfaces. The role of hierarchical and complex surface topography in nature is to amplify the hydrophobicity and maximize the fouling resistance. Thus, a similar micro- and nano-scale 3-D topographic surfaces inspired from the nature were fabricated using a simple and scalable two roll coating process. This process was based on the ribbing instabilities associated with the shearing of non-Newtonian fluids between two rollers. The polymer composite retains the deformed shape due to the recovery of high-viscosity after removing the shear stress. The relationship between the process conditions and the textured structure were studied with the shear rate, capillary number and the surface roughness parameters (e.g., Wenzel factor and density of peaks). The results showed that the samples’ Wenzel roughness factor increased with the increase in shear rate up to a particular value and then decreased. Similarly, the density of peaks in the sample increased with an increase in capillary number up to a particular value and then decreased. These bioinspired surfaces with hierarchical textured patterns produced using two roll coating process show a tremendous potentiality to be used in super-hydrophobic, anti-biofouling, and drag reduction applications.