(476h) Jamming in Complex Fluids: Effects of Surface-Active Agents on Interfacial Transport

The behaviour of oil-water interfaces in the presence of surface-active agents holds significant importance across diverse industrial and environmental domains¹ such as emulsion stabilization² and oil recovery processes.³ By influencing interfacial dynamics, these agents can also contribute to the jamming phenomenon, where interfacial structures impede displacement within confined geometries. This work focuses on understanding how surface-active agents induce or mitigate jamming, the mechanisms governing this behaviour, and their impact on transport processes in complex fluid systems.

In this study, we employ coarse-grained Dissipative Particle Dynamics (DPD)^4-7 simulations to investigate the influence of surfactants and nanoparticles (NPs) on meniscus behavior within a nanochannel under controlled flow conditions. Special emphasis is placed on amphiphilic Janus nanoparticles (JPs), which exhibit both hydrophilic and hydrophobic characteristics. The reservoir channel was modeled with a bottleneck structure to represent a constricted region within the channel. Our simulations reveal that the presence of NPs and surfactants significantly alters meniscus shape, movement, and the onset of jamming within a bottleneck-shaped channel. The displacement process follows a four-phase progression as the flow rate increases: an initial equilibrium phase, first interface jamming, second interface jamming at a critical flow rate, and a final phase where jamming ceases at extremely high flow rates. By systematically analyzing the effects of interfacial composition, capillary pressure, and channel geometry, we provide insights into how the jamming process occurs to optimize transport through confined spaces. In addition, the presence of NPs and surfactants affects not only the shape and movement of the meniscus but also the position where jamming occurs. It is observed that the presence of surfactants can reduce the energy requirement, whereas the NP layer may lead to a challenge in the movement of the interface. The location of the meniscus jamming relative to the nanochannel stenosis can be predicted either by a force balance or by minimizing the energy of the system. The most notable finding is that jamming does not occur at the narrowest section of the channel but instead takes place just beyond this constriction. Regarding the effect of NP, the rearrangement of NPs after the jamming occurs also observed at the jamming point.

These findings enhance our understanding of NP behavior at oil-water interfaces, offering valuable guidance for optimizing fluid transport and interfacial control in industrial and environmental applications. The computational methodology, validation, and implications of our results for interfacial engineering will be discussed in detail.

References

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