The research is motivated by the quest to understand the tensile stresses exerted by liquids within small channels and to help mitigate the problem of "stiction" that is prevalent in micro and nano scale devices. Measurements of flow rate, tensile force, surface deformation and friction force will be performed for interfaces involving liquid interposed between solid bodies of prescribed surface roughness. In parallel with the experiments, a mathematical model will be developed that considers elastic deformation and capillary effects to describe the flow of a thin liquid film at the interface between contacting rough, elastic surfaces. This work will assess the validity of the notion of interface collapse as predicted by recently published mathematical models in the literature. This investigation will also serve to establish new lower bounds on the magnitude of negative capillary pressures generated in narrow interfaces. Results of the work are anticipated to have relevance to several technical areas, including those related to flow in porous media, the stability of wet soils, MEMS, magnetic recording, adhesives, and seals. Additionally, the project will provide enriched educational experiences for undergraduate and pre-college students. Undergraduate researchers will be involved in developing a video entitled "Capillary Connections" that features several physical demonstrations of capillarity, touching on several disparate areas, such as the stick-slip behavior of wiper blades, the ascent of water in plants, the function of adhesives, and mechanisms of absorption in porous bodies (like common sponges). It is planned to make the video publicly accessible by posting at YouTube. Leveraging the NSF-sponsored STEP program at Georgia Tech, undergraduate and graduate students supported by the proposed project will visit STEP partner high schools to show and discuss the Capillary Connections video.
