Light scattering was used to measure the time-dependent loss of air entrapped within a submerged microporous hydrophobic surface subjected to different environmental conditions. The loss of trapped air resulted in a measurable decrease in surface reflectivity and the kinetics of the process was determined in real time and compared to surface properties, such as porosity and morphology. The light-scattering results were compared with measurements of skin-friction drag, static contact angle, and contact-angle hysteresis. The in situ, noninvasive optical technique was shown to correlate well with the more conventional methods for quantifying surface hydrophobicity, such as flow slip and contact angle.

Metallic tubes have been synthesized by a polymer-based template approach using electroless deposition. Gold, copper, and nickel were deposited as thin films on sub-micrometer polymer fibers which ranged in diameter from approximately 160 to 400 nm. After thermal degradation of the template fibers at 300 and 650 degrees C, tubes between 450 and 730 nm were obtained with wall thicknesses of 50-150 nm. Characterization by scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and powder X-ray diffraction indicate that the tubes have a face-centered cubic structure with [111] preferred orientation for all of the metals investigated and that the tube walls are polycrystalline, composed of nanoparticles, ranging in size from 5.0 to 25.0 nm.

Mesh-like fiber mats of polystyrene (PS) were deposited using DC-biased AC-electrospinning. Superhydrophobic surfaces with water contact angles greater than 150and gas fraction values of up to 97% were obtained. Rheological study was conducted on these fiber surfaces and showed a decrease in shear stress when compared with a noncoated surface (no slip), making them excellent candidates for applications requiring the reduction of skin-friction drag in submerged surfaces. We have also shown that addition of a second, low-surface energy polymer to a solution of PS can be used to control the fiber internal porosity depending on the concentration of the second polymer. Contact-angle measurements on mats consisting of porous and nonporous fibers have been used to evaluate the role of the larger spaces between the fibers and the pores on individual fibers on superhydrophobicity.

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Submicrometer ZnO tubes have been synthesized by a polymer based template approach using sol-gel deposition. Zinc acetate, a precursor to ZnO, was deposited on catalytically active electrospun polycarbonate fibers approximately 250+/-100 nm in diameter. Thermal degradation of the core fibers resulted in the oxidation of zinc acetate to produce ZnO nanotubes with diameters of approximately 500+/-100 nm and an average wall thickness of approximately 100+/-50 nm. Scanning electron microscopy (SEM), Energy dispersive spectroscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and UV-visible spectroscopy were used to characterize the composition, structure, and morphology of the tubes. Powder X-ray diffraction results showed that a wurtzite crystalline phase was obtained. The UV-visible absorption spectrum was red-shifted by 25 nm due to narrowing of the ZnO band gap (approximately 3.22 eV) as a result of Co doping. Similarly, green band emission was not observed in the emission spectrum, while emission lifetime was determined to be 620 ps from photoluminescence studies.