Dissipation of Film Drainage Resistance by Hydrophobic Surfaces in Aqueous Solutions

Understanding and minimizing the film drainage resistance (forces) from a moving fluid are of great importance both scientifically and technologically. The direct and accurate measurement of film drainage resistance was made possible by integrating a speaker diaphragm of large displacement range and rapid responses with a sensitive bimorph force sensor and high resolution digital camera: Our study demonstrates that the liquid :film drainage resistance can be greatly diminished or accurately controlled by increasing or controlling the hydrophobicity of solid surfaces. The results show that for a given solid surface hydrophobicity, the film drainage resistance at the point where film ruptures increases linearly with increasing bubble approach velocity. The dependence of the film drainage. resistance on bubble :approach velocity decreases linearly with increasing hydrophobicity of the solid surface. This finding has important implications for biological processes, microfluidic devices, and design of new materials.