The evaporation of surfactant-laden droplets: A comparison between contact line models

Gaalen, R.T. van; Diddens, Christian; Wijshoff, Herman; Kuerten, Johannes G.M.

doi:10.1016/j.jcis.2020.06.099

Cited by 15 publications

(8 citation statements)

References 61 publications

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“…The consideration of surfactants in numerical simulations of evaporating droplets requires a sophisticated treatment of the surfactant concentration field at the curved, moving and shrinking interface 87 and its coupling to the bulk field via ad-and desorption processes. Recently, however, simulations of evaporating droplets containing insoluble 92,93 and soluble surfactants 94 have been accomplished. In this latest work, the surface tension is assumed to follow a Frumkin equation of state with the surfactant concentration, taking into account steric interactions among the surfactants.…”

Section: Solutal Marangoni Flow Due To Surface Active Materialsmentioning

confidence: 99%

Evaporation-driven liquid flow in sessile droplets

2022

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Section: Solutal Marangoni Flow Due To Surface Active Materialsmentioning

confidence: 99%

Evaporation-driven liquid flow in sessile droplets

2022

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“…In contrast to the homogeneous droplet shrinking for the solvent, the polymer mixture effectively showed a pinned contact line that causes a decrease in contact angle. In the literature, numerical simulations of droplet evaporation with insoluble surfactants explained this behavior with the decrease in surface tension near the contact line due to the increase of surfactant concentration that could not equilibrate fast enough via diffusion 30 . Also experimentally, the dynamic contact angle could be shown to decrease with increasing surfactant concentration in aqueous solution 31 .…”

Section: Discussionmentioning

confidence: 98%

“…In the literature, numerical simulations of droplet evaporation with insoluble surfactants explained this behavior with the decrease in surface tension near the contact line due to the increase of surfactant concentration that could not equilibrate fast enough via diffusion. 30 Also experimentally, the dynamic contact angle could be shown to decrease with increasing surfactant concentration in aqueous solution. 31 However, in the case of a PDMS based gutter layer surface, this was not observable in our experiments and the drop of the contact angle to 30 was very similar for both the pure solvent and polymer solution.…”

Section: Surface Energy Effects At the Phaseinterfacesmentioning

confidence: 97%

Numerical and experimental investigation of the unexpected thickening effect during PolyActive™ coating of TFC membranes

Brennecke,

Clodt,

Brinkmann

et al. 2024

J Adv Manuf & Process

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In this work, we used a previously described computational fluid dynamics (CFD) model of a roll‐to‐roll coating process for the fabrication of thin‐film composite membranes to predict the final coating thickness for PolyActive™, a commercially available multiblock copolymer utilized for CO2 removal membranes. We found a strong thickening effect that could not be explained by our previous model. We investigated the process experimentally. In addition, we conducted a variety of simulations with extensions of the initial CFD model. Based on our findings, we conclude that the Marangoni effect, that is, gradients of surface tension that induce secondary flow patterns in the meniscus region, is the most likely source of the observed thickening. We explain the simulation results in order to understand the physical mechanisms at play and to show how especially surface tension gradients that arise from the particular flow structure in the meniscus may explain the additional transfer of polymer solution to the membrane. Finally, we draw some conclusions on future research and give ideas on future improvements of the process. To our knowledge, Marangoni effects for the coating of PolyActive™ were not described so far in the literature, even though it is a well‐known polymer for gas separation membranes targeted at CO2 removal. Roll‐to‐roll coating is a well‐established coating method and often believed to be suitable for the scale‐up of membrane production, therefore we think that this work will help membrane researchers who are using similar coating devices to be cautious about possible complications in the process.

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“…[33][34][35] However, the physics of the problem is very complicated in such a way that different types of surfactants can have different effects on the interfacial flow of evaporating sessile droplets. 36 It was shown that insoluble surfactants do not produce Marangoni vortices, 37 but soluble surfactants can drive considerable recirculation. 38 Considering that Marangoni eddies can lead to unexpected distributions of solute particles 39 and have a tremendous impact on the deposition, 40 this contribution benefits from the results of the previous research done by our group.…”

Section: Introductionmentioning

confidence: 99%