Droplet Fusion in Oil-in-Water Pickering Emulsions.

Catherine P Whitby,Floriane Bahuon

doi:10.3389/fchem.2018.00213

Abstract

We have formed compound droplets made of two or more drops of immiscible oils by temporarily destabilizing Pickering oil-in-water emulsions. The emulsions used are synergistically stabilized by mixtures of cationic surfactant and negatively-charged particles. They are highly sensitive to the concentration of surfactant present in the emulsions. We took advantage of transient droplet coalescence events that are triggered by reducing the surfactant concentration to fuse together drops of immiscible oils. This study provides guidelines for designing compound droplets by transient (or limited) coalescence in Pickering emulsions. We show that the possible geometries of particle-stabilized compound drops are determined by the interfacial tensions and relative volumes of the drops fused together. The implications of our results for designing strategies to fabricate multiphase drops are discussed.

Highlights

Compound droplets consist of drops of two immiscible fluids that have been fused together (Johnson and Sadhal, 1985; Neeson et al, 2012)
Oil-in-water emulsions were stabilized by mixtures of hydrophilic fumed silica nanoparticles (Wacker Chemie N20) and hexadecyltrimethyl ammonium bromide (CTAB, 99% purity, Sigma Aldrich)
We studied fusion in oil-in-water emulsions stabilized by mixtures of negatively charged silica nanoparticles and a cationic surfactant, hexadecyltrimethyl ammonium bromide

Summary

Introduction

Compound droplets consist of drops of two (or more) immiscible fluids that have been fused together (Johnson and Sadhal, 1985; Neeson et al, 2012). Novel configurations, such as Janus droplets, can form under the extreme flow conditions achieved in microfluidic channels (Choi et al, 2013) These developments have rejuvenated interest in designing robust and convenient routes for fusing drops of immiscible liquids together on a scale larger than that achieved in microfluidic channels (Hasinovic and Friberg, 2011; Fryd and Mason, 2014; Weyer et al, 2015; Ge et al, 2017; Wei et al, 2017). In this brief report, we describe a new approach that uses nanoparticles to control the fabrication of drops with multiple compartments

Methods

Results

Conclusion