Ultimate jumping of coalesced droplets on superhydrophobic surfaces

Yuan, Zhiping; Gao, Sihang; Hu, Zhifeng; Dai, Liyu; Hou, Huimin; Chu, Fuqiang; Wu, Xiaomin

doi:10.1016/j.jcis.2020.12.007

Cited by 41 publications

(23 citation statements)

References 42 publications

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“…3c shows the relationship between the energy-conversion efficiency and the coalescence mismatch after two-droplet coalescence (Supplementary Movie 4 ). The results are calculated using the customized VOF solver JumpingFOAM based on OpenFOAM, which is particularly designed to handle jumping droplet simulations 52 , 53 (Supplementary Discussion 7 ). The initial configurations of a single droplet of being in touch with the lattice bottom or being suspended on the top of the lattice, are predicted theoretically.…”

Section: Resultsmentioning

confidence: 99%

Condensation droplet sieve

Chen

Wang

et al. 2022

Nat Commun

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Large droplets emerging during dropwise condensation impair surface properties such as anti-fogging/frosting ability and heat transfer efficiency. How to spontaneously detach massive randomly distributed droplets with controlled sizes has remained a challenge. Herein, we present a solution called condensation droplet sieve, through fabricating microscale thin-walled lattice structures coated with a superhydrophobic layer. Growing droplets were observed to jump off this surface once becoming slightly larger than the lattices. The maximum radius and residual volume of droplets were strictly confined to 16 μm and 3.2 nl/mm2 respectively. We reveal that this droplet radius cut off is attributed to the large tolerance of coalescence mismatch for jumping and effective isolation of droplets between neighboring lattices. Our work brings forth a strategy for the design and fabrication of high-performance anti-dew materials.

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Section: Resultsmentioning

confidence: 99%

Condensation droplet sieve

Chen

Wang

et al. 2022

Nat Commun

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“…Wang et al reported a millimetric triangular prism macrotexture and achieved a maximum droplet jumping velocity V j * = 0.53, with an energy conversion efficiency η ≈ 22.49% . In addition, rectangular ridge structures, curved surfaces, hydrophobic fibers, strings, and V-shaped structures , have been used to obtain a higher jumping velocity and break the velocity limit. Furthermore, Yuan et al used the impact between the liquid bridge and the bottom, flank side of the L-shaped macrotexture.…”

Section: Introductionmentioning

confidence: 99%

Enhancement and Guidance of Coalescence-Induced Jumping of Droplets on Superhydrophobic Surfaces with a U-Groove

Liu

Zhao

Zheng

et al. 2021

ACS Appl. Mater. Interfaces

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Coalescence-induced droplet jumping has received considerable attention owing to its potential to enhance performance in various applications. However, the energy conversion efficiency of droplet coalescence jumping is very low and the jumping direction is uncontrollable, which vastly limits the application of droplet coalescence jumping. In this work, we used superhydrophobic surfaces with a U-groove to experimentally achieve a high dimensionless jumping velocity V j * ≈ 0.70, with an energy conversion efficiency η ≈ 43%, about a 900% increase in energy conversion efficiency compared to droplet coalescence jumping on flat superhydrophobic surfaces. Numerical simulation and experimental data indicated that a higher jumping velocity arises from the redirection of in-plane velocity vectors to out-of-plane velocity vectors, which is a joint effect resulting from the redirection of velocity vectors in the coalescence direction and the redirection of velocity vectors of the liquid bridge by limiting maximum deformation of the liquid bridge. Furthermore, the jumping direction of merged droplets could be easily controlled ranging from 17 to 90°by adjusting the opening direction of the U-groove, with a jumping velocity V j * ≥ 0.70. When the opening direction is 60°, the jumping direction shows a deviation as low as 17°from the horizontal surface with a jumping velocity V j * ≈ 0.73 and corresponding energy conversion efficiency η ≈ 46%. This work not only improves jumping velocity and energy conversion efficiency but also demonstrates the effect of the U-groove on coalescence dynamics and demonstrates a method to further control the droplet jumping direction for enhanced performance in applications.

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“…Recently, the energy conversion efficiency has been further increased to around 50% using surface structures, including fibers, 23 triangular prism, 24 and egg tray-like structure. 25 of liquid bridge impact and the in-plane momentum, which can thus be converted into the perpendicular component more effectively. However, such an approach requires the scrupulous position control of precedent drops, such that the liquid bridge forms directly above the surface feature.…”

Section: ■ Introductionmentioning

confidence: 99%

High-Efficiency Directional Ejection of Coalesced Drops on a Circular Groove

Liu

et al. 2022

Langmuir

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Coalescence-induced drop jumping has received significant attention in the past decade. However, its application remains challenging as a result of the low energy conversion efficiency and uncontrollable drop jumping direction. In this work, we report the high-efficiency coalescenceinduced drop jumping with tunable jumping direction via rationally designed millimeter-sized circular grooves. By increasing the surface-droplet impact site area and restricting the oscillatory deformation, the energy conversion efficiency of the jumping droplet reaches 43.5%, 600% as high as the conventional superhydrophobic surfaces. The droplet jumping direction can be tuned from 90°to 60°by varying the principal curvature of the circular groove, while the energy conversion efficiency remains unchanged. We show through theoretical analysis and numerical simulations that the directional jumping mainly originates from reallocation of droplet momentum enabled by the asymmetric liquid bridge impact. Our study demonstrates a simple yet effective method for fast, efficient, and directional droplet removal, which warrants promising applications in jumping droplet condensation, water harvesting, anti-icing, and self-cleaning.

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Ultimate jumping of coalesced droplets on superhydrophobic surfaces

Cited by 41 publications

References 42 publications

Condensation droplet sieve

Condensation droplet sieve

Enhancement and Guidance of Coalescence-Induced Jumping of Droplets on Superhydrophobic Surfaces with a U-Groove

High-Efficiency Directional Ejection of Coalesced Drops on a Circular Groove

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