Six Stages of Microdroplet Detachment from Microscale Fibers

The detachment of droplets from cylindrical fibers is of fundamental importance for both scientific research and engineering applications. Due to the challenges to determine dynamic contact angles on the fiber surface, the process of the droplet detachment from a fiber is not well understood. In this paper, a multibody dissipative particle dynamics (MDPD) method, a particle-based mesh-free method that can automatically capture the dynamic contact angles through direct modeling of liquid-solid particle interactions, was applied to study the detachment process of a liquid microdroplet from a cylindrical solid fiber pulled by an atomic force microscopy (AFM) tip under a constant velocity. After the validation of the numerical results through comparison with experiments in a benchmark case, the same numerical tool was applied to analyze the droplet detachment mechanisms. Based on the slope of the time history curve for the displacement of the droplet mass center, the detachment process can be divided into six stages. The change of slope in each stage can be explained from the change of surface energy. The results can greatly advance the fundamental understanding of the detachment process of microdroplets from cylindrical fibers.