A Simple Non-Embedded Single Capillary Device for On-Demand Complex Emulsion Formation

This study includes an examination of the design, fabrication, and experimentation of a rudimentary droplet generator. The device has potential applications in on-demand double and higher-order emulsions as well as tailored emulsions with numerous cores. The phenomenon of a pendant double droplet creation is observed when an inner phase is transported through a capillary, while a middle phase envelops the external surface of the capillary. This leads to the occurrence of a pinching-off process at the tip of the pulled capillary. Following this, the double droplet is introduced into a container that is filled with the outer phase. The present study examines the force equilibrium throughout the droplet break-up process and aims to forecast the final morphology of the droplets within the container by considering the impact of interfacial tension ratios. The shell thickness in a core-shell formation can be calculated based on the inner and middle phase flow rates as well as the middle droplet formation period. The present platform, which enables the simple production of double and higher emulsions, exhibits promising prospects for the controlled manufacturing of complex emulsions. This technology holds potential for various applications, including the experimental exploration of collision behavior or electro-hydrodynamics in emulsions as well as millimeter-size engineered microparticle fabrication.