Asymmetric coalescence-induced droplet jumping on hydrophobic fibers

Li, Bingbing; Feng, Xin; Zhu, Guorui; Tan, Wei

doi:10.1016/j.ces.2019.02.041

Cited by 5 publications

(5 citation statements)

References 41 publications

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“…Comparing Figure with Figure a, it can be found that in C 7 H 8 , the morphology evolution and the overall coalescence time of the merged droplets were similar to those in n -C 6 H 14 , but the number of coalescence stages was only four stages, and the coalescence time of each stage was longer than that in n -C 6 H 14 . It is well known that the driving force for the droplet morphology and droplet jumping is excess surface energy, which is proportional to the oil–water interfacial tension. , As shown in Table , the oil–water interfacial tension of C 7 H 8 is 35.7 mN/m, which is only about 70.7% that of n -C 6 H 14 . Hence, the frequency of droplet morphology evolution in C 7 H 8 was lower than that in n -C 6 H 14 , i.e., the time required for each stage of droplet deformation was larger than that in n -C 6 H 14 , as shown in Figure .…”

Section: Resultsmentioning

confidence: 99%

“…It is well known that the driving force for the droplet morphology and droplet jumping is excess surface energy, which is proportional to the oil−water interfacial tension. 27,28 As shown in Table 1, the oil−water interfacial tension of C 7 H 8 is 35.7 mN/m, which is only about 70.7% that of n-C 6 H 14 . Hence, the frequency of droplet morphology evolution in C 7 H 8 was lower than that in n-C 6 H 14 , i.e., the time required for each stage of droplet deformation was larger than that in n-C 6 H 14 , as shown in Figure 6.…”

Section: Effect Of Bulk Fluid Viscositymentioning

confidence: 99%

“…Droplet jumping behavior can be influenced not only by the microstructures of hydrophobic surfaces − and the characteristic of droplets − but also by the bulk fluids surrounding the droplets. − However, most of the work was limited to studying the behavior of water droplet coalescence and jumping in the air, and few mention the effects of bulk fluids on the droplet coalescence and jumping behavior. It has been reported that the properties of the bulk fluid can affect the merged behaviors of droplets.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Dynamics of Droplet Coalescence on Hydrophobic Fibers in Oil: Morphology and Liquid Bridge Evolution

Li¹,

Tan

Liu³

et al. 2023

ACS Omega

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Although droplet self-jumping on hydrophobic fibers is a well-known phenomenon, the influence of viscous bulk fluids on this process is still not fully understood. In this work, two water droplets’ coalescence on a single stainless-steel fiber in oil was investigated experimentally. Results showed that lowering the bulk fluid viscosity and increasing the oil–water interfacial tension promoted droplet deformation, reducing the coalescence time of each stage. While the total coalescence time was more influenced by the viscosity and under-oil contact angle than the bulk fluid density. For water droplets coalescing on hydrophobic fibers in oils, the expansion of the liquid bridge can be affected by the bulk fluid, but the expansion dynamics exhibited similar behavior. The drops begin their coalescence in an inertially limited viscous regime and transition to an inertia regime. Larger droplets did accelerate the expansion of the liquid bridge but had no obvious influence on the number of coalescence stages and coalescence time. This study can provide a more profound understanding of the mechanisms underlying the behavior of water droplet coalescence on hydrophobic surfaces in oil.

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Section: Resultsmentioning

confidence: 99%

Section: Effect Of Bulk Fluid Viscositymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Dynamics of Droplet Coalescence on Hydrophobic Fibers in Oil: Morphology and Liquid Bridge Evolution

Li¹,

Tan

Liu³

et al. 2023

ACS Omega

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“…Droplet coalescence jumping could facilitate droplets to leave superhydrophobic surfaces spontaneously, which has extensive prospects in self-cleaning, − energy harvesting, − atmospheric corrosion protection, , and anti-icing/frosting. , In those applications, the jumping direction and velocity are important factors affecting the performance. The jumping velocity V j of the coalescence of two equal-sized droplets follows the capillary-inertial scaling. , Previous studies have demonstrated that size mismatch, quantity, and distribution have a negligible effect on jumping direction. , Nevertheless, the jumping velocity is less than that of when two equal-sized droplets coalesced. ,− …”

Section: Introductionmentioning

confidence: 93%

Exploration of Sweeping Effect: Droplet Coalescence Jumping of a Rolling and Static Droplet

Liu,

Zhao,

Guo

et al. 2024

Langmuir

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The sweeping effect of merged droplets plays a key role in enhancing application performance due to the continuing coalescence caused by the horizontal jumping velocity. Most studies focused on static droplet coalescence jumping, while moving droplet coalescence is poorly understood. In this work, we experimentally and numerically study the coalescence of a rolling droplet and a static one. When the droplet radius ratio is larger than 0.8, as the dimensionless initial velocity increases and the vertical jumping velocity first decreases and then increases. The critical dimensionless initial velocity V c * corresponding to the minimum vertical jumping velocity could be estimated as . When the droplet radius ratio is smaller than 0.8, the dimensionless initial velocity has a positive effect on the vertical jumping velocity. The mechanism of the vertical jumping velocity can be attributed to two parts: liquid bridge impact and retraction of the merged droplet. The squeezing effect generated by the initial velocity between the two droplets promotes the growth of the liquid bridge and enhances the impact effect of the liquid bridge but weakens the upward velocity accumulation caused by the retraction of the merged droplets. However, different from the vertical jumping velocity, the horizontal jumping velocity is approximately proportional to the dimensionless initial velocity. The outcome of our work elucidates a fundamental understanding of a rolling droplet coalescing with a static one.

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“…Nanodroplets have wide applications in various fields such as the self‐assembly of nanomaterials, fluid transport, catalysis, and 3D nanoinkjet printing . In these applications, coalescence is a significant process as it determines the formation and evolution of the droplet . Moreover, it has been widely observed and shown that the size distribution of droplets is dominated by coalescence .…”

Section: Introductionmentioning

confidence: 99%

Time‐dependent density functional study for nanodroplet coalescence

Niu

Liu

et al. 2019

AIChE Journal

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The coalescence of nanodroplets is an important interfacial phenomenon and is the key to many real-world applications. However, the microscopic mechanism for this process remains unclear. In this work, we propose a time-dependent density functional theory (TDDFT) to understand and predict this process. The formation of a "peanut" nanodroplet seems key to the coalescence process, before and after which the system is dominated by a nucleation mechanism and an ordinary diffusion mechanism, respectively. It appears that molecular attraction is not only the driving force but also the resistance of droplet coalescence. The velocity distribution indicates that there is a significant mass transfer on the vapor-liquid interphase. During coalescence, there is a clear linear correlation between the free energy and the surface area of the vapor-liquid interface, which means surface tension is the dominant contribution to the free energy.

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Asymmetric coalescence-induced droplet jumping on hydrophobic fibers

Cited by 5 publications

References 41 publications

Dynamics of Droplet Coalescence on Hydrophobic Fibers in Oil: Morphology and Liquid Bridge Evolution

Dynamics of Droplet Coalescence on Hydrophobic Fibers in Oil: Morphology and Liquid Bridge Evolution

Exploration of Sweeping Effect: Droplet Coalescence Jumping of a Rolling and Static Droplet

Time‐dependent density functional study for nanodroplet coalescence

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