Marangoni instability triggered by selective evaporation of a binary liquid inside a Hele-Shaw cell

Cruz, Ricardo Arturo Lopez de la; Diddens, Christian; Zhang, Xuehua; Lohse, Detlef

doi:10.1017/jfm.2021.555

Cited by 9 publications

(13 citation statements)

References 64 publications

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“…The flow inside the arches is depicted with black arrows and shown with streak lines in Figure b for the case of c tA = 0.416. Such a flow with pairs of convective rolls is typical of Marangoni instabilities. ,,, In our case, the presence of the air–liquid interface and the lower surface tension of volatile ethanol are the origin of the instability, in accordance with previous predictions. , For further details in the conditions needed for the instability to be triggered, see the SI.…”

Section: Results and Discussionsupporting

confidence: 90%

“…Based on the experimental measurements by using optical microscopy, a Marangoni instability occurs at the early stage of the evaporation process, regardless of the initial composition of the solutions. The instability and the induced convective rolls are in accordance with linear stability predictions for binary solutions in two-dimensional and quasi-two-dimensional models. Depending on the initial concentration of the ternary mixtures, the duration and the effect of the Marangoni instability on the subsequent liquid–liquid phase separation vary significantly.…”

Section: Discussionsupporting

confidence: 78%

“…Similarly to binary ethanol–water mixtures, x F increases approximately as a power law while the instability is active. For low oil contents (blue group), the exponent of the power law is close to 1/2, as in the binary case . For the rest of the cases, the exponent is larger, up to 0.7 (see the SI).…”

Section: Results and Discussionmentioning

confidence: 78%

“…Following the pioneering works of Sternling and Scriven and Linde et al, our recent work from Lopez de la Cruz et al showed that evaporation of a binary solution from an open side of a Hele-Shaw cell can trigger complicated flow dynamics, in particular, a Marangoni instability. In this case, selective evaporation creates a gradient in concentration normal to the gas–liquid interface.…”

Section: Introductionmentioning

confidence: 99%

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Phase Separation of an Evaporating Ternary Solution in a Hele-Shaw Cell

et al. 2021

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In the present work, we investigate the dynamic phenomena induced by solvent evaporation from ternary solutions confined in a Hele-Shaw cell. The model solutions consist of ethanol, water, and oil, and with the decrease in ethanol concentration by selective evaporation, they may undergo microdroplet formation via the ouzo effect or macroscopic liquid–liquid phase separation. We varied the initial concentration of the three components of the solutions. For all ternary solutions, evaporation of the good solvent ethanol from the gas–liquid interface, aligned with one side of the cell, leads to a Marangoni instability at the early stage of the evaporation process. The presence of the Marangoni instability is in agreement with our recent predictions based on linear stability analysis of binary systems. However, the location and onset of subsequent microdroplet formation and phase separation are the result of the interplay between the Marangoni instability and the initial composition of the ternary mixtures. We classified the ternary solutions into different groups according to the initial concentration of oil. For each group, based on the ternary diagram of the mixture, we offer a rationale for the way phase separation takes place and discuss how the instability influences droplet nucleation. Our work helps us to understand under what conditions and where droplet nucleation can take place when advection is present during phase separation inside a microfluidic device.

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Section: Results and Discussionsupporting

confidence: 90%

Section: Discussionsupporting

confidence: 78%

Section: Results and Discussionmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

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Phase Separation of an Evaporating Ternary Solution in a Hele-Shaw Cell

et al. 2021

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“…It is reminiscent of the convective rolls inside the arch-shaped patterns observed in an evaporative ethanol–water binary system confined in a Hele-Shaw cell, which is driven by a Marangoni instability caused by the gradient of ethanol at the interface (Linde, Pfaff & Zirkel 1964; de la Cruz et al. 2021). However, in our case, the generation of the convective rolls follows a different route.…”

Section: Stage Ii: Evolution Of Segregative Patterns and Induced Loca...mentioning

confidence: 99%

Physiochemical hydrodynamics of the phase segregation in an evaporating binary microdroplet

Diddens

et al. 2022

J. Fluid Mech.

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Phase segregation triggered by selective evaporation can emerge in multicomponent systems, leading to complex physiochemical hydrodynamics. Recently, Li et al. (Phys. Rev. Lett., vol. 120, 2018, 224501) and Kim & Stone (J. Fluid Mech., vol. 850, 2018, pp. 769–783) reported a segregative behaviour (i.e. demixing) in an evaporating binary droplet. In this work, by means of experiments and theoretical analysis, we investigate the flow dynamics after the occurrence of the phase segregation. As example, we take the 1,2-hexanediol–water binary droplet system. First, we reveal experimentally the overall physiochemical hydrodynamics of the evaporation process, including the segregative behaviour and the resulting flow structure close to the substrate. By quantifying the evolution of the radial flow, we identify three successive life stages of the evaporation process. At Stage I, a radially outward flow is observed, driven by the Marangoni effect. At the transition to Stage II, the radial flow reverses partially, starting from the contact line. This flow breaks the axial symmetry and remarkably is driven by the segregation itself. Finally at Stage III, the flow decays as the evaporation ceases gradually. At this stage, the segregation has grown to the entire droplet, and the flow is again controlled by the Marangoni effect. The resulting Marangoni flow homogenizes the distribution of the entrapped volatile water over the whole droplet.

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