Coalescence of dispersed micrometer-scale droplets is an essential step toward the separation of emulsions. The thin film between droplets must form, drain, and rupture for coalescence to occur. In surfactant-stabilized emulsions, the film drainage and droplet coalescence processes are known to be hindered because of reduced interfacial mobility. However, a clear correlation between this mobility and the underlying surfactant transport and interfacial response to shear and dilatational deformations is undercharacterized. For microscale droplets, the effect of surfactant transport to the interface and along the interface is often difficult to isolate from other bulk effects on emulsion stability. In this work, we review surfactant-mitigated coalescence in both macroscale and microscale experiments, highlighting the importance of interfacial curvature and length scales when establishing a correlation between coalescence theory and film mobility.
Bibliographical noteFunding Information:
The authors would like to thank Dr. Raymond Dagastine from the University of Melbourne and Dr. Sibani Lisa Biswal from Rice University for the invitation to submit this manuscript to COCIS. This work was partially supported by the NSF through the University of Minnesota Materials Research Science and Engineering Center (MRSEC) under Award Numbers DMR-1420013 and DMR-2011401 . S.N. and R.B. were supported by Donaldson Company Inc . (Bloomington, MN). R.B. was also supported by a Department of Mechanical Engineering fellowship at the University of Minnesota. A.M. was supported by a National Science Foundation (NSF) Graduate Research Fellowship. T.N. was supported by the Strategic Environmental Research and Development Program (SERDP) project WP18-1031 . Portions of this work were conducted in the Minnesota Nano Center, which is supported by the National Science Foundation through the National Nano Co-ordinated Infrastructure Network (NNCI) under Award Number ECCS-2025124 . There are no conflicts of interest to declare. The authors would also like to thank Dr. Yun Chen at the University of Minnesota as well as collaborators at Donaldson Company, including Dr. Davis Moravec, Dr. Brad Hauser, and Dr. Andrew Dallas, for helpful discussions.
- Interfacial rheology
- Thin films