Bubble Meets Droplet: Particle‐Assisted Reconfiguration of Wetting Morphologies in Colloidal Multiphase Systems

Abstract

Wetting phenomena are ubiquitous in nature and play key functions in various industrial processes and products. When a gas bubble encounters an oil droplet in an aqueous medium, it can experience either partial wetting or complete engulfment by the oil. Each of these morphologies can have practical benefits, and controlling the morphology is desirable for applications ranging from particle synthesis to oil recovery and gas flotation. It is known that the wetting of two fluids within a fluid medium depends on the balance of interfacial tensions and can thus be modified with surfactant additives. It is reported that colloidal particles, too, can be used to promote both wetting and dewetting in multifluid systems. This study demonstrates the surfactant-free tuning and dynamic reconfiguration of bubble-droplet morphologies with the help of cellulosic particles. It further shows that the effect can be attributed to particle adsorption at the fluid interfaces, which can be probed by interfacial tensiometry, making particle-induced transitions in the wetting morphology predictable. Finally, particle adsorption at different rates to air-water and oil-water interfaces can even lead to slow, reentrant wetting behavior not familiar from particle-free systems.

Advanced Switchable Molecules and Materials for Oil Recovery and Oily Waste Cleanup

“…For example, Zhang et al reported that the addition of appropriate colloidal particles can change the wetting configurations significantly. [211] Clearly, there are many research opportunities on the fundamental understandings of oil engulfment phenomenon, especially for the systems involving high viscosity oils, which is essential not only for the improvement of oil desorption efficiency on novel UV-RAs, but also for many industrial applications, such as flotation-assisted oil recovery, contrastenhanced ultrasonography, and defoaming.…”

Manipulation of gas-liquid-liquid systems in continuous flow microreactors for efficient reaction processes

“…2d-e) are generated when γ t-r is relatively small. Herein, one of the dispersed phases having a larger interfacial force with the carrier fluid will be engulfed into the other dispersed phase, implying that for gas-liquidliquid flow bubbles are (often) encapsulated in droplets since it is energetically favorable [54].…”

“…Due to the high analogy between two-phase (gas-liquid or liquid-liquid) and three-phase (gas-liquid-liquid) microflows [17], the established transport knowledge in the former case certainly sheds important light herein. It is thus expected that the balance among interfacial, inertial and viscous forces also plays an important role in determining the phase dispersion within three-phase flow through microreactors [13,23,43,50,53,54]. This implies that for designing and studying three-phase microflow, some important parameters (e.g., capillary number, Weber number and Reynolds number, the phase flow rate ratios) deserve much research attention [18,50].…”

Four reversible and reconfigurable structures for three-phase emulsions: extended morphologies and applications

“…Janus emulsions, because of their natural asymmetric ability in the compositions and the shapes, are often used in the fields that need asymmetry in the shape and the materials. In these Janus materials, organic-inorganic composite 11 , nanoparticles 12 , and gas bubbles 13 are often used to achieve specific functions. But the close relationship between morphologies and the components might restrict the application of specific components combination or restrict the components choice range for the specific morphology.…”

“…The dynamical transformation from Janus to core-shell evolution is also achieved in flowing state 21 . Small particles, which could disperse at the interface of different phases, also have been used to achieve the reconfiguration of bubble core-shell structure to Janus structure 12 . From all these results, we found that the separate transformation between different Janus structures, core-shell to reverse core-shell structures, Janus to core-shell structures, or core-shell to Janus structures have been achieved by different research groups.…”