Effects of stripy surfaces with intervals on the coalescence dynamics of nano-droplets: Insights from molecular dynamics simulations

Li, Tao; Xia, Yujie; Zhang, Lishu; Zhang, Xingfan; Fu, Chengrui; Jiang, Yanyan; Li, Hui

doi:10.1016/j.apsusc.2019.03.120

Cited by 27 publications

(10 citation statements)

References 47 publications

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“…To further elucidate the effect of temperature, the mean-square displacement of the droplet atoms in the x -direction (MSD x ) is plotted, as depicted in Figure . This approach has also been utilized in prior studies to demonstrate the effect of temperature or substrate features , on molecular displacement and diffusion. It is evident from Figure that increase in temperature leads to greater displacement along the dominant direction of spreading, i.e., the x -direction.…”

Section: Resultsmentioning

confidence: 99%

Molecular Investigation of Contact Line Movement in Electrowetted Nanodroplets

2020

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Molecular dynamics (MD) simulation of an electrowetted nanodroplet is performed to understand the fundamental origin of the involved parameters resulted from the molecular movement in the vicinity of the three-phase contact line (TPCL). During the spreading of the droplet, contact line friction (CLF) force is found to be the controlling one among all other resistive forces. Being molecular in nature, MD study is required to unveil the CLF, which is manifested by the TPCL friction coefficient ζ. The combined effect of temperature, electric field, and surface wettability, manifested by the solid–liquid Lennard-Jones interaction parameter, is studied to explore the droplet spreading. The entire droplet wetting dynamics is divided into two different regimes, namely, spreading regime and equilibrium regime. The molecular frequency during the TPCL movement in the equilibrium regime is affected by the presence of any external perturbation and results in an alteration of ζ. The predetermined knowledge of the alteration of CLF due to the coupling effect of electric field and temperature will have a potential application towards designing electric field-inspired droplet movement devices.

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Section: Resultsmentioning

confidence: 99%

Molecular Investigation of Contact Line Movement in Electrowetted Nanodroplets

2020

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“…Since the differences between conventional flat superhydrophobic surfaces and textured superhydrophobic surfaces lie in the existence of textures, their layout should significantly affect the wall wetting behavior and hence droplet dynamics. − Shi et al showed that droplet jumping could be promoted by increasing the texture height or decreasing their spacing . Gao et al performed molecular dynamics simulations and showed that nanodroplets prefer to jump away from those surfaces with decreased surface wettability intensity and solid fraction .…”

Section: Introductionmentioning

confidence: 99%

Critical and Optimal Wall Conditions for Coalescence-Induced Droplet Jumping on Textured Superhydrophobic Surfaces

et al. 2019

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The effectiveness of coalescence-induced jumping of microdroplets on superhydrophobic surfaces is critical to a wide range of applications such as self-cleaning surfaces, anti-icing/frosting, water harvesting, phase-change heat transfer, and hotspot cooling. Introducing textures on the surfaces can readily enlarge the effective contact angle, while an overlarge texture spacing may unfavorably lead to droplet penetration into the gaps in droplet coalescence processes. To clarify the effect of surface textures on the droplet jumping dynamics, we simulated the coalescence of droplets on textured superhydrophobic surfaces with various surface wettability and texture spacings and theoretically derived the critical conditions of jumping and the optimal condition of maximum jumping velocity. The results show that the nonmonotonic emergence of "nonjumping"−"jumping"−"nonjumping" with decreasing solid fraction is synergistically controlled by the surface adhesion and the effective impinging pressure. At a large solid fraction, the transition from "nonjumping" to "jumping" is caused by the reduction of the dimensionless surface adhesion energy below a critical value, which is determined to be 0.035 for Oh = 0.02 and 0.01 for Oh = 0.12. At a small solid fraction, the transition from "jumping" to "nonjumping" is dominated by the reduction of the dimensionless effective impinging pressure, the critical value of which is identified to be 0.14 and is independent of Oh. Moreover, jumping velocity maximizes when wetting critically transits from the Cassie−Baxter (CB) state to the partial-wetting state, and a penetration index is proposed from the wetting theory to predict such transition, which shows good agreement with both present simulations and previous experiments. The present findings are helpful for the design of superhydrophobic surfaces that pursue robust and efficient jumping of droplets.

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“…Furthermore, by reasonably designing the substrates with nanopillars that show an arrangement density gradient, the coalescence dynamics, such as the final position or adhesion of the coalesced droplets, the coalescence speed, the shape evolution of the coalescing droplets, could be accurately controlled. Besides, heterogeneous superhydrophobic surfaces decorated with many micropatterned pillars have also been designed for achieving coalescence-induced self-jumping of the droplets. − The surfaces decorated with nanostripe structures have also been designed to tune the coalescing behaviors, which also belongs to one kind of surface protruding structure when compared to the smooth surfaces . According to the abovementioned studies, it could be learned that the surface microstructure plays an essential role in the regulation of coalescence dynamics.…”

Section: Introductionmentioning

confidence: 99%

“…27−32 The surfaces decorated with nanostripe structures have also been designed to tune the coalescing behaviors, which also belongs to one kind of surface protruding structure when compared to the smooth surfaces. 33 According to the abovementioned studies, it could be learned that the surface microstructure plays an essential role in the regulation of coalescence dynamics. However, existing studies mainly focus on the design of micro-/nanopillars to modify the substrate surface, while the substrates decorated with some new and potential microstructures receive less attention and deserve to be explored for controlling coalescence behaviors.…”

Section: ■ Introductionmentioning

confidence: 99%

Controllable Coalescence Dynamics of Nanodroplets on Textured Surfaces Decorated with Well-Designed Wrinkled Nanostructures: A Molecular Dynamics Study

Zhang

2021

Langmuir

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The control of coalescence and motion of droplets play a significant role in advanced technology and our daily life, and one of the most important approaches is surface design. Here, the microtextured surfaces decorated with wrinkled substrates are designed and studied for coalescence behaviors. The simulation results show that the coalescence speed would be slower on such surfaces due to the downward movement of the droplets induced by the penetration of atoms into the grooves that delays their movement along the coalescence direction, which is considered as a restriction effect. With the increase of the angles and the interval distance of wrinkled structures, the coalescence time becomes longer and the coalescing process becomes unfavorable, resulting from the enhanced restriction effect. More importantly, a composite substrate possessing the original and sub-wrinkled structures has been designed to tune the coalescence dynamics. The results of this work may not only help shed light on understanding the coalescence behaviors on the wrinkled substrates but also propose a feasible method for controlling the liquid coalescence behavior, which is expected to provide some useful implications for practical applications.

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Effects of stripy surfaces with intervals on the coalescence dynamics of nano-droplets: Insights from molecular dynamics simulations

Cited by 27 publications

References 47 publications

Molecular Investigation of Contact Line Movement in Electrowetted Nanodroplets

Molecular Investigation of Contact Line Movement in Electrowetted Nanodroplets

Critical and Optimal Wall Conditions for Coalescence-Induced Droplet Jumping on Textured Superhydrophobic Surfaces

Controllable Coalescence Dynamics of Nanodroplets on Textured Surfaces Decorated with Well-Designed Wrinkled Nanostructures: A Molecular Dynamics Study

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