Dynamical wetting transition of a stretched liquid bridge

Abstract

The liquid bridge is an important model problem in printing processes. We report the experimental results of stretching a highly viscous liquid bridge between two parallel plates. Depending on the stretching speed, a thin liquid bridge exhibits two representative flow regimes. At low stretching speeds, the liquid bridge deforms in a quasi-static manner and no liquid films are observed. When the stretching speed exceeds a critical value, the contact line fails to follow the retracting meniscus, resulting in the deposition of liquid films on the plate. The entrained film is characterized by an annular rim that retracts and grows by collecting the liquid in the film. It is found that the velocity of the receding contact line is weakly decreasing, and the growth of the rim is characterized by a width of wrim∼Ca1/3t1/2, where the capillary number Ca is defined by the stretching velocity and t is the time. The film may not be fully absorbed into the bulk of the liquid bridge before its eventual breakup at high stretching speeds, leading to variations in the liquid transfer ratio of the two plates.