Control of wettability transition and coalescence dynamics of droplets on the surface via mechanical vibration: A molecular simulation exploration

Tao, Li; Li, Jie; Lin, Hao; Duan, Yunrui; Xia, Yujie; Jiang, Yanyan; Li, Hui

doi:10.1016/j.apsusc.2018.12.171

Cited by 37 publications

(11 citation statements)

References 40 publications

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“…Therefore, the possible methods to move the water bridge are in two different ways. One way is the change of surface property (Walker et al, 2017;Li et al, 2019), making the water bridge desorb from the kerogen surface, and the second way is made by weakening the interaction between different H 2 O molecules. Actually, this is similar to the operations in the development of petroleum (changing the wettability and reducing the viscosity).…”

Section: Spatial Distribution Of Ch 4 and Comentioning

confidence: 99%

Stability analysis of the water bridge in organic shale nanopores: A molecular dynamic study

Liu¹,

Zhang²,

Sun³

2022

Capillarity

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In the last decades, shale gas development has relieved the global energy crisis and slowed global warming problems. The water bridge plays an important role in the process of shale gas diffusion, but the stability of the water bridge in the shale nanochannel has not been revealed. In this work, the molecular dynamics method is applied to study the interaction between shale gas and water bridge, and the stability can be tested accordingly. CO 2 can diffuse into the liquid H 2 O phase, but CH 4 only diffuses at the boundary of the H 2 O phase. Due to the polarity of H 2 O molecules, the water bridge presents the wetting condition according to model snapshots and one-dimensional analyses, but the main body of the water bridge in the two-dimensional contour shows the non-wetting condition, which is reasonable. Due to the effect of the molecular polarity, CO 2 prefers to diffuse into kerogen matrixes and the bulk phase of water bridge. In the bulk of the water bridge, where the interaction is weaker, CO 2 has a lower energy state, implies that it has a good solubility in the liquid H 2 O phase. Higher temperature does not facilitate the diffusion of CO 2 molecules, and higher pressure brings more CO 2 molecules and enhances the solubility of CO 2 in the H 2 O phase, in addition, a larger ratio of CO 2 increases its content, which does the same effects with higher pressures. The stability of the water bridge is disturbed by diffused CO 2 , and its waist is the weakest position by the potential energy distribution.

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Section: Spatial Distribution Of Ch 4 and Comentioning

confidence: 99%

Stability analysis of the water bridge in organic shale nanopores: A molecular dynamic study

Liu¹,

Zhang²,

Sun³

2022

Capillarity

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“…Self-propelled droplet jumping on superhydrophobic surfaces has been attracting considerable attention due to its practical relevance to various applications such as self-cleaning surfaces, anti-icing/frosting surfaces, , water harvesting, phase-change heat transfer, − thermal diodes, and hotspot cooling . Compared to the rebound of the impacting droplet and the jumping of the droplet on vibrating surfaces, the self-propelled jumping of coalesced droplets is spontaneous without consuming any external energy. Instead, such self-propelled jumping is induced by the conversion of released excess surface energy to translational kinetic energy during droplet coalescence, in the presence of the symmetry-breaking action from droplet–substrate interaction. − Previous studies on flat superhydrophobic surfaces showed that droplet diameters ranging from micrometer to millimeter could jump off the surface, , with the jumping velocity peaking at droplet radius R 0 of approximately 50 μm.…”

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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“…Considerable work has been done to investigate the drop coalescence process, for both theoretical and experimental studies. − For example, Wang et al , studied the coalescence behavior of two adjacent conducting drops when an electric field is applied and found that the drops may completely coalesce, partially coalesce, or bounce off one another, which mainly depends on the strength of the electric field. Roy investigated the coalescence preference dynamics during nonequilibrium phase separation of a single-component fluid by using molecular dynamics simulations and suggested that the relative coalescence position exhibits a power-law dependence on the parent size ratio with an exponent q ≈ 3.1.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Study of the Temperature-Dependent Coalescence of Liquid Nanodrops: Implications for Microfluidics

Zhang

et al. 2019

ACS Appl. Nano Mater.

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Drop coalescence is central to diverse processes involving microfluidics in industrial, engineering, and scientific realms and has attracted much attention in recent years. Here, the effect of temperature on the coalescence of liquid nanodrops is investigated by using molecular dynamics simulations. Our data give visible evidence that the increase of temperature positively promotes the coalescence process featured by the enhanced mixing degree, resulting from the larger diffusion of atoms. More importantly, the temperature difference can affect the coalescence way, and therefore three metastable models of the coalesced nanodrop are found during coalescence, which are “uniform” type, “segregation” type, “wrapped” type. Interestingly, for the identical nanodrop, its diffusion can be enhanced when coalescing with a high-temperature nanodrop but restricted with a low-temperature nanodrop, which indicates the possibility of tuning coalescence by a temperature-controlled method. Besides, other temperature systems are also considered for further studying the effect of temperature, such as the same temperature-difference system. This work would provide a comprehensive molecular-level view of the effect of the temperature on the coalescence of liquid nanodrops and open up new ways to control microfluidics for some applications.

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Control of wettability transition and coalescence dynamics of droplets on the surface via mechanical vibration: A molecular simulation exploration

Cited by 37 publications

References 40 publications

Stability analysis of the water bridge in organic shale nanopores: A molecular dynamic study

Stability analysis of the water bridge in organic shale nanopores: A molecular dynamic study

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

Molecular Dynamics Study of the Temperature-Dependent Coalescence of Liquid Nanodrops: Implications for Microfluidics

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