Coalescence of Pickering emulsion droplets induced by an electric field

TL;DR

This study investigates how electric fields induce coalescence in Pickering emulsion droplets, revealing two distinct mechanisms influenced by particle shell defects, with implications for controlling emulsion stability.

Contribution

It uncovers the role of particle shell defects in electrocoalescence behavior, distinguishing between normal and abnormal coalescence mechanisms.

Findings

Normal coalescence involves continuous liquid bridge growth.

Abnormal coalescence features spontaneous bridge breakup.

Defect size in particle shells determines coalescence type.

Abstract

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.