Plateau-Rayleigh Instability and Capillary Droplet Propulsion on a Fiber*

The Plateau-Rayleigh instability (PRI) of a liquid column underlies a variety of hydrodynamic phenomena. Compared to the classical case of a free liquid column, the description of a liquid layer on a fiber requires the consideration of the solid-liquid interface in addition to the free surface. We revisit the PRI of a liquid layer on a solid fiber by varying the hydrodynamic boundary condition at the fiber-liquid interface from no-slip to slip. We find that the growth rate depends on the system geometry and the boundary condition, which is in agreement with theory. In the late stages of liquid column breakup on slip-fibers, a three-phase contact line can be formed on one side of the droplet. The resulting capillary imbalance leads to droplet propulsion, which is studied as a function of temperature and molecular weight.