  Droplets coalescing on flat surfaces tend to end up with the smaller droplet
migrating into the larger one. We report a counter-intuitive droplet
coalescence pattern on a superhydrophilic cylindrical wire, where the larger
droplet is pulled toward the smaller one. Consequently, the center of the
combined mass significantly moves toward, often beyond, the original location
of the smaller droplet. This phenomenon occurs primarily because the viscous
friction that a droplet experiences on a cylindrical wire is not positively
correlated with the size of the droplet, unlike the droplets coalescing on flat
surfaces. We conducted a dimensional analysis based on a mass-spring-damper
(MSD) model. Our model predicts a variety of coalescence patterns as a function
of the ratio between droplet sizes, and the prediction matches the experimental
observation.
