Flow profiles near receding three-phase contact lines: influence of surfactants

Straub, Benedikt B.; Schmidt, Henrik; Rostami, Peyman; Henrich, Franziska; Rossi, Massimiliano; Kähler, Christian J.; Butt, Hans‐Jürgen; Auernhammer, Günter K.

doi:10.1039/d1sm01145f

Cited by 3 publications

(2 citation statements)

References 59 publications

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“…Meanwhile, it has been demonstrated before that even tiny gradients in the surface tension of the liquid can induce substantial changes in dynamic contact angles and thus drop motion. 39 After 1000 drops, the drop velocity started to increase, and finally, it reached a velocity of 0.39 m/s ± 0.03 m/s after 4 cm, which is close to that on PDMS-0. This verifies that the continuous drop sliding on the surface removes lubricant.…”

Section: Resultssupporting

confidence: 69%

“…Such a Marangoni effect is largely independent of clocking layer thickens, this is constant with our experimental results (Figure S7 in the Supporting Information). Meanwhile, it has been demonstrated before that even tiny gradients in the surface tension of the liquid can induce substantial changes in dynamic contact angles and thus drop motion . After 1000 drops, the drop velocity started to increase, and finally, it reached a velocity of 0.39 m/s ± 0.03 m/s after 4 cm, which is close to that on PDMS-0.…”

Section: Resultssupporting

confidence: 52%

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Spontaneous Charging of Drops on Lubricant-Infused Surfaces

Bista

Weber

et al. 2022

Langmuir

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When a drop of a polar liquid slides over a hydrophobic surface, it acquires a charge. As a result, the surface charges oppositely. For applications such as the generation of electric energy, lubricant-infused surfaces (LIS) may be important because they show a low friction for drops. However, slide electrification on LIS has not been studied yet. Here, slide electrification on lubricant-infused surfaces was studied by measuring the charge generated by series of water drops sliding down inclined surfaces. As LIS, we used PDMS-coated glass with micrometer-thick silicone oil films on top. For PDMS-coated glass without lubricant, the charge for the first drop is highest. Then it decreases and saturates at a steady state charge per drop. With lubricant, the drop charge starts from 0, then it increases and reaches a maximum charge per drop. Afterward, it decreases again before reaching its steady-state value. This dependency is not a unique phenomenon for lubricant-infused PDMS; it also occurs on lubricant-infused micropillar surfaces. We attribute this dependency of charge on drop numbers to a change in surface conductivity and depletion of lubricant. These findings are helpful for understanding the charge process and optimizing solid–liquid nanogenerator devices in applications.

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Section: Resultssupporting

confidence: 69%

Section: Resultssupporting

confidence: 52%

Spontaneous Charging of Drops on Lubricant-Infused Surfaces

Bista

Weber

et al. 2022

Langmuir

Self Cite

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Adsorption layer and flow within liquid meniscus in forced dewetting

Kovalchuk

Auernhammer

2023

Current Opinion in Colloid & Interface Science

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Three-dimensional internal flow evolution of an evaporating droplet and its role in particle deposition pattern

Li,

Hong

2024

Physics of Fluids

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The internal flow within an evaporating sessile droplet is one of the driving mechanisms that lead to various particle deposition patterns seen in applications such as inkjet printing, surface patterning, and blood stain analysis. Despite decades of research, the causal link between droplet internal flow and particle deposition patterns has not been fully established. In this study, we employ a three-dimensional (3D) imaging technique based on digital inline holography to quantitatively assess the evolution of internal flow fields and particle migration in three distinct types of wetting droplets, namely water droplets, sucrose aqueous solution droplets, and sodium dodecylsulfate aqueous solution droplets, throughout their entire evaporation process. Our imaging reveals the three-stage evolution of the 3D internal flow regimes driven by changes in the relative importance of capillary flow, Marangoni flow, and droplet boundary movement during evaporation. Moreover, the migration of individual particles from their initial locations to deposition can be divided into five categories, with some particles depositing at the contact line and others inside the droplet. In particular, we observe the changing migration directions of particles due to competing Marangoni and capillary flows. We further develop an analytical model that predicts the droplet internal flow, deposition patterns, and determines the deposition mechanisms depending on their initial locations and evolving internal flow. The model, validated using different types of droplets from our experiment and the literature, can be further expanded to other Newtonian and non-Newtonian droplets, potentially serving as a real-time assessment tool for particle deposition in various applications.

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Flow profiles near receding three-phase contact lines: influence of surfactants

Abstract: The dynamics of wetting and dewetting is largely determined by the velocity field near the contact lines. For water drops it has been observed that adding surfactant decreases the dynamic...

Cited by 3 publications

References 59 publications

Spontaneous Charging of Drops on Lubricant-Infused Surfaces

Spontaneous Charging of Drops on Lubricant-Infused Surfaces

Adsorption layer and flow within liquid meniscus in forced dewetting

Three-dimensional internal flow evolution of an evaporating droplet and its role in particle deposition pattern

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