Wetting of liquid droplets on two parallel fibers with different radii

The spreading behavior of liquid droplets bridged by filaments is theoretically studied in this work. In our model, the wetted droplets between the fibers can be in one of three different equilibrium morphologies: barrel, bridge, or liquid column. The results show that small-volume droplets undertake a reversible column-to-bridge transformation. However, two distinct transitions are observed for large-volume droplets: column-to-bridge transition in the case of separated fibers and bridge-to-barrel-to-column transition for closely spaced fibers. Particular attention is paid to a hysteretic behavior of large-volume droplets at various inter-fiber distances. It is found that the our results are in good agreement with available experimental data.