(757a) Evolution of Non-Axisymmetric Capillary Bridges Between Chemically Heterogeneous Surfaces

Investigations of capillary bridge morphologies are traditionally focus on relatively simple geometries on chemically homogeneous surfaces. Chemical heterogeneities, however, pin drops on surfaces and this pinning alters the shape and energy of capillary bridges. Here we describe the morphological transitions of capillary bridges pinned on chemically heterogeneous surfaces. More specifically, we study capillary bridges pinned on long wetting stripes patterned on non-wetting surfaces. The wetting stripes have a high aspect ratio (length/width ≈ 60), which means that the capillary bridges formed are highly asymmetric and somewhat similar to a slit-pore geometry. We have characterized the shape, associated force, and stability for the bridges as a function of the channel geometry and liquid volume. We observe a morphological transition for the capillary bridges when the ratio of the height/width of the bridge is of order unity. More specifically we observe a transition between concave to convex in the bridges’ curvature as the two surfaces are pulled apart. We also provide scaling arguments for these morphological changes, generalizing our results to a wide range of potential geometries. Finally, we obtain good agreement between our experimental results and theoretical predictions based on a simple surface free energy function and energy minimization.