Growth and arrest of the cusp formed by coalescing yield stress drops

Yield stress fluids are ubiquitous in everyday life and burgeoning in research. Here we experimentally investigate the evolution of the cusp formed by two coalescing yield stress fluid drops using high speed imaging technology. In the short-time post coalescence the formed liquid bridge grows self-similarly balanced by viscosity and surface tension. At long-time the drop's liquid-gas interface arrests in a non-equilibrium shape influenced by yield stress. The influence of yield stress, contact angle and contact angle symmetry on these initial coalescence dynamics and on the final non-equilibrium rest state of the post-coalesced drops will be discussed, and our results compared against a numerical model for the cusp evolution.