  Combining high-speed photography with electric current measurement, we
investigate the electrocoalescence of Pickering emulsion droplets. Under high
enough electric field, the originally-stable droplets coalesce via two distinct
approaches: normal coalescence and abnormal coalescence. In the normal
coalescence, a liquid bridge grows continuously and merges two droplets
together, similar to the classical picture. In the abnormal coalescence,
however, the bridge fails to grow indefinitely; instead it breaks up
spontaneously due to the geometric constraint from particle shells. Such
connecting-then-breaking cycles repeat multiple times, until a stable
connection is established. In depth analysis indicates that the defect size in
particle shells determines the exact merging behaviors: when the defect size is
larger than a critical size around the particle diameter, normal coalescence
will show up; while abnormal coalescence will appear for coatings with smaller
defects.
