Dynamic super menisci: spontaneous film climbing of colloidal particle solutions

We report experiments showing that suspensions can form a “super meniscus” above a critical interfacial concentration of particles. As a pre-wetted film is inserted into a liquid interface covered with particles, we observe a climbing liquid front as well as a lagging particle front. Previously, the Marangoni effect has been used to produce the growth of climbing films, where a surface tension gradient drives flow with the aid of temperature, surfactant or solute gradients. Particles at an interface may also change the effective interfacial properties. A high-speed interferometric technique is used to track in-situ the film thickness of a climbing colloidal solution. We find that the particle size and particle concentration control the rising and falling rates of the climbing film as well as the final deposition patterns of the particles. We also present a mathematical model to rationalize our results.