Anti-fog coatings using the super-hydrophobic approach

The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file and two media files.Title from title screen of research.pdf file (viewed on August 10, 2009)Thesis (M.S.) University of Missouri-Columbia 2008.Surfaces with water contact angles in excess of 150[degrees] have been attracting a great deal of attention. The work done here was in the design and development of an anti-fog coating. The hydrophilic as well as the hydrophobic approaches were investigated before developing the super-hydrophobic coatings. Accordingly, various phenomenon such as the adherence of snow or raindrops and friction drag are expected to be inhibited or reduced on such surfaces. Hydrophobic properties are enhanced by increasing surface roughness. Superhydrophobic surfaces require both appropriate surface roughness and low surface energy materials and numerous methods to attain these requirements have been demonstrated. We have made extensive use of nano-particles to help us in achieving the roughness that was needed to create these super-hydrophobic surfaces. Also low surface energy materials such as PTFE and THV were investigated as potential candidates for the matrix materials in which the particles could be embedded. The films created in our labs were characterized extensively using SEM(Scanning Electron Microscopy), Water Contact angles, Spectroscopic Ellipsometry, AFM(Atomic Force Microscopy) and UV-VIS Spectroscopy.Includes bibliographical references

Non-volatile liquid-film-embedded microfluidic valve for microscopic evaporation control and contactless bio-fluid delivery applications

Quick evaporation speed of microfluids can cause many unexpected problems and failures in various microfluidic devices and systems. In this dissertation, a new evaporation speed controlling method is demonstrated using a thin liquid-film based microfluidic valve. Microfluidic droplet ejectors were designed, fabricated and integrated with the liquid-film based microfluidic valve. The thin liquid film with nonvolatility and immiscibility exhibited excellent microfluidic valve functionality without any stiction problem between valve components, and provided a very effective evaporation protection barrier for the microfluids in the device. Successful evaporation control by the liquid-film-embedded (LiFE) microfluidic valve has been demonstrated. In addition, guided actuation of the microfluidic valve along predefined paths was successfully achieved using newly developed oil-repellent surfaces, which were later used for developing ‘virtual walls’ for confining low surface tension liquids within predefined areas. Moreover, bioinspired slippery surfaces for aiding the microfluidic valve along the ejector surface have also been developed. These slippery surfaces were evaluated for their effectiveness in reducing microfluidic valve driving voltages. Finally, a sliding liquid drop (SLID) shutter technique has been developed for a normally closed functionality with aid from nanostructures. The SLID shutter resolves many issues found in the previous LiFE microfluidic valve. Smooth and successful printing results of highly volatile bio-fluids have been demonstrated using the SLID shutter technique. I envision that these demonstrated techniques and developed tools have immense potential in various microfluidic applications