Coalescence and spreading of drops on liquid pools

Kulkarni, Varun; Lolla, Venkata Yashasvi; Tamvada, Suhas; Shirdade, Nikhil; Anand, Sam

doi:10.1016/j.jcis.2020.10.089

Cited by 16 publications

(11 citation statements)

References 65 publications

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“…The strength of the viscous effects was related to the properties of the liquid, and the viscous effects could be evaluated by the Ohnesorge number in the liquid properties function, Oh D / lg 0 μ ρσ = . 43 According ). H b is the index for quantitative analysis of the vertical deformation strength of droplets.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…In the process of droplet retraction and rebound, the pinning position was the main part of energy consumption, which was mainly due to viscous dissipation. The strength of the viscous effects was related to the properties of the liquid, and the viscous effects could be evaluated by the Ohnesorge number in the liquid properties function, . According to the shear viscosity data of the solution, the viscosity of each treatment varied greatly at a low shear rate, while there was no difference between different treatments at a high shear rate (Figure S2).…”

Section: Resultsmentioning

confidence: 99%

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Optimization Strategy to Inhibit Droplets Rebound on Pathogen-Modified Hydrophobic Surfaces

Ding

et al. 2021

ACS Appl. Mater. Interfaces

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The deposition and retention of pesticide sprays on the surface of hydrophobic plant leaves is a major agricultural challenge, and the deposition of hydrophobic surfaces caused by plant leaf diseases is also a major agricultural problem. Many recent studies have focused on evaluating the effect of adding surfactants to water rather than to pesticide solutions to increase the deposition and retention of spray liquids. Here, we report a strategy to solve the problem of deposition and retention by studying the impact of the behavior of pesticide droplets with added surfactants and performing kinetic analysis on cucumber leaves with powdery mildew. The reduction in the bounce and splash of the pesticide droplets was analyzed by combining the pinning site formed in the retraction stage and the viscous dissipation in the rebound stage. In the practical application of the pesticide spray, we can clearly see that the bounce, splash, and powdery mildew spore ejection decreased when surfactants were added to the pesticide spray that was used on the cucumber leaves, and the adhesion and retention increased. The proposed comprehensive method is helpful for understanding the interactions between pesticide spray droplets and the surface of cucumber leaves with powdery mildew.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Optimization Strategy to Inhibit Droplets Rebound on Pathogen-Modified Hydrophobic Surfaces

Ding

et al. 2021

ACS Appl. Mater. Interfaces

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“…Once the initial contact is developed between the droplets, the droplet contour is described by the evolution of bridge height, h b , perpendicular to the substrate and bridge width, r m , parallel to the substrate. In the case of Newtonian fluids, potential technological interest has driven a lot of effort in investigating the effects of surface wettability, [6][7][8] surface deformity, 9 viscosity, 10,11 droplet size, 12,13 and contact angle hysteresis 14,15 on the growth of meniscus bridge at both initial and later stages of the coalescence. In particular, Narhe et al 16 proposed a scaling of h b $ t and r m $ t 1=2 for initial stages of coalescence, where the capillary number (Ca) was greater than 0.2.…”

Section: Introductionmentioning

confidence: 99%

Elasticity can affect droplet coalescence

2022

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Coalescence of two droplets on a solid substrate is an interfacial phenomenon that imposes the challenges of capturing the complex contact line motion and energy interaction between the solid-liquid interface. Recent investigations on the coalescence of polymeric droplets on a solid substrate have reported strong disagreements; the heart of the issue is whether coalescence of polymeric drops is similar to that of Newtonian fluid and is independent of molecular relaxation, or whether the role of entanglement of polymeric chains leads to a transition kinetics different from that of Newtonian fluid. Via this article, we resolve the disagreements through a discussion on the effects of merging method on the dominant forces governing the coalescence process, i.e., inertia, dissipation, and relaxation. In this regard, two methods of merging have been identified, namely droplet spreading method (DSM) and volume filling method (VFM). Our study unveils that the coalescence dynamics of polymeric drops is not universal and in fact, is contingent of the method by which the coalescence is triggered. Additionally, we demonstrate the spatial features of the bridge at different time instants by a similarity analysis. We also theoretically obtain a universal bridge profile by employing the similarity parameter in a modified thin film lubrication equation for polymeric fluids.

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“…On-drop chemistry has been increasingly explored for fine chemical production based on biphasic reactions, the synthesis of novel bio- and nanomaterials, fast and sensitive chemical analysis, and engineering chemorobotic platforms. − Notably, many reactions confined in the droplets have been reported to be faster than on a large scale. The reaction rates may be enhanced by 10 2 to even 10 6 times compared to reactions in the bulk. − Droplet reactions may also simplify postpurification processes for a wide range of biphasic reactions where reactants or products are present in two immiscible fluid phases, such as oil and water or liquid and gas. − Microdroplet chemistry is considered to be green and sustainable, enabling efficient chemical conversion for a wide range of reactants under mild reaction conditions or without using metal, heat, or expensive catalysts …”

Section: Introductionmentioning

confidence: 99%

Growth Rates of Hydrogen Microbubbles in Reacting Femtoliter Droplets

Zeng

Zhang

2022

Langmuir

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Chemical reactions in small droplets are extensively explored to accelerate the discovery of new materials and increase the efficiency and specificity in catalytic biphasic conversion and high-throughput analytics. In this work, we investigate the local rate of the gas-evolution reaction within femtoliter droplets immobilized on a solid surface. The growth rate of hydrogen microbubbles (≥500 nm in radius) produced from the reaction was measured online with high-resolution confocal microscopic images. The growth rate of bubbles was faster in smaller droplets and near the droplet rim in the same droplet. The results were consistent for both pure and binary reacting droplets and on substrates of different wettability. Our theoretical analysis based on diffusion, chemical reaction, and bubble growth predicted that the concentration of the reactant depended on the droplet size and the bubble location inside the droplet, in good agreement with experimental results. Our results reveal that the reaction rate may be spatially nonuniform in the reacting microdroplets. The findings may have implications for formulating the chemical properties and uses of these droplets.

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Coalescence and spreading of drops on liquid pools

Cited by 16 publications

References 65 publications

Optimization Strategy to Inhibit Droplets Rebound on Pathogen-Modified Hydrophobic Surfaces

Optimization Strategy to Inhibit Droplets Rebound on Pathogen-Modified Hydrophobic Surfaces

Elasticity can affect droplet coalescence

Growth Rates of Hydrogen Microbubbles in Reacting Femtoliter Droplets

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