Self Assembled, Ultra-Hydrophobic Micro/Nano-Textured Surfaces

Report No. ARL-TN-275
Authors: Adam M. Rawlett; Joshua A. Orlicki; Nicole Zander; Afia Karikari; Tim Long
Date/Pages: April 2007; 24 pages
Abstract: The formation of hierarchically ordered arrays of spherical cavities on polymer films is of interest due to potential applications in the preparation of photonic bandgaps materials, environmental sensors, and patterned light-emitting diodes. While many methods are known for the preparation of these porous materials, the breath figure approach has received significant scrutiny because of the simple and robust mechanism of pattern formation. Breath figures are patterned arrays of micrometer-sized defects in a polymer film, formed when water droplets condense onto a polymer solution surface during film drying. By controlling variables such as relative humidity and solvent, the feature size and uniformity of the resultant pattern can be controlled. The breath figure approach is valuable because it is versatile, inexpensive, and provides the advantages of large area ordering in the nano and micrometer regime. The self assembly of regular arrays of nano and microscale pores in polymer matrices generated using the breath figure technique is being explored. Experimental parameters are modified to vary the size, spacing, organization, and long-range order of these self-organizing surfaces. Utilizing these regular arrays of pores as templates, we have patterned analogous arrays of pillars (inverse pores) from a polymer film cast onto the patterned surface. These micro/nano-textured surfaces have enhanced the hydrophobicity of the textured polymer when measured by contact angle. This method of producing ultra-hydrophobic textured surfaces should be amenable to high-throughput, low-cost manufacturing of myriad polymeric surfaces.
Distribution: Approved for public release
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Last Update / Reviewed: April 1, 2007