Wetting and electrowetting on corrugated substrates

Wang, Zhanlong; Zhao, Ya‐Pu

doi:10.1063/1.4984244

Cited by 43 publications

(14 citation statements)

References 47 publications

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“…After the maximum spreading, the droplet contact line pins at the edge of the wall of the hexagonal cavity. Similar behavior of the pinning of the contact line was reported on a corrugated surface and surface with protruded sharp edges, by Wang and co-workers 15,26 . While the droplet rebounds, the surface energy converts into the kinetic energy.…”

Section: Droplet Impact Dynamics Taro Leafsupporting

confidence: 83%

“…They varied the pitch of the grooves and droplet impact velocity, and reported different fates of the impacting droplet, namely, no-bouncing, partial bouncing and complete bouncing. Wang and Zhao 15 and Wang et al 16 also experimentally investigated anisotropic wetting characteristics of corrugated and microgrooves surfaces, respectively. In these studies, they reported a strong dependence of the contact angle on the geometry of the grooves.…”

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confidence: 99%

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Wetting characteristics of Colocasia esculenta (Taro) leaf and a bioinspired surface thereof

Kumar

Bhardwaj

2020

Sci Rep

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We investigate wetting and water repellency characteristics of Colocasia esculenta (taro) leaf and an engineered surface, bioinspired by the morphology of the surface of the leaf. Scanning electron microscopic images of the leaf surface reveal a two-tier honeycomb-like microstructures, as compared to previously-reported two-tier micropillars on a Nelumbo nucifera (lotus) leaf. We measured static, advancing, and receding angle on the taro leaf and these values are around 10% lesser than those for the lotus leaf. Using standard photolithography techniques, we manufactured bioinspired surfaces with hexagonal cavities of different sizes. The ratio of inner to the outer radius of the circumscribed circle to the hexagon (b/a) was varied. We found that the measured static contact angle on the bioinspired surface varies with b/a and this variation is consistent with a free-energy based model for a droplet in cassie-Baxter state. the static contact angle on the bioinspired surface is closer to that for the leaf for b/a ≈ 1. However, the contact angle hysteresis is much larger on these surfaces as compared to that on the leaf and the droplet sticks to the surfaces. We explain this behavior using a first-order model based on force balance on the contact line. finally, the droplet impact dynamics was recorded on the leaf and different bioinspired surfaces. The droplets bounce on the leaf beyond a critical Weber number (We ~ 1.1), exhibiting remarkable water-repellency characteristics. However, the droplet sticks to the bioinspired surfaces in all cases of We. At larger We, we recorded droplet breakup on the surface with larger b/a and droplet assumes full or partial Wenzel state. The breakup is found to be a function of We and b/a and the measured angles in full Wenzel state are closer to the predictions of the free-energy based model. the sticky bioinspired surfaces are potentially useful in applications such as waterharvesting. Superhydrophobic and hydrophobic surfaces have generated significant interest in the last two decades due to their potential technical applications in designing functional surfaces that exhibit properties such as self-cleaning, low drag, antifouling, water harvesting, anti-icing etc. 1-5. In order to design such functional non-wetting surfaces, several researchers have been inspired by non-wetting characteristics of leaves of different species of plants. A remarkable example is a lotus leaf, that exhibits non-wetting characteristics due to the presence of micro-and nanoscale features on its surface. A notable review by Neinhuis and Barthlott 6 compiled published data of wetting characteristics and morphology of leaves of around 200 plants. In particular, they attributed non-wetting characteristics to microstructures and wax present on the surface. Similarly, Koch et al. 7 and Koch and Barthlott 8 discussed diversity in the morphology of the surface of the leaves of the different plants and their role in determining the wetting characteristics. These reviews also discuss how to engineer or biomimic a...

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Section: Droplet Impact Dynamics Taro Leafsupporting

confidence: 83%

mentioning

confidence: 99%

Wetting characteristics of Colocasia esculenta (Taro) leaf and a bioinspired surface thereof

Kumar

Bhardwaj

2020

Sci Rep

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“…This case was classified as ''Mixed Pinning". On the surfaces of plenty of natural and industrial products (e.g., micro channels [51], leaves of plants [52][53][54] and feather of birds [55]), the second and third states are most common. In these cases, the contact line is difficult to cross the defects, leading to the directional spreading of the droplet along the grooves on channeled surfaces [5], or the immersion of liquids on super-hydrophobic surfaces.…”

Section: Discussionmentioning

confidence: 99%

The effect of sharp solid edges on the droplet wettability

Wang

Lin

Zhao

2019

Journal of Colloid and Interface Science

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Understanding the role of pinning force in droplet dynamic wetting is of critical importance for surface science studies. Generally, the pinning force is only related to the surface tension and the change of contact angle. However, there is an obvious correlation between the pinning force and the surface geometry. In this paper, the relation between the surface geometry and contact line pinning was studied with systematical experiments and theoretical analysis. We compared the samples with different edge angles and carried out plenty experiments with different liquids. Meanwhile, the theoretical analysis and molecular simulation were carried out. The results show that the sharp edge has a strong pinning effect on the contact line and can significantly change the contact angle and wetting state of droplets. The maximum contact angle of droplet has a linear relation with the edge angle of substrate. The formula of pinning force was revised to consider the impact of surface topography. According to the relationship between surface defect and contact line, we proposed a model to classify the cases of contact line pinning for the first time. Our research will deepen the understanding of contact line pinning and provide help for potentially industrial production designs.

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“…为了探究非极性C−C键与极性B−N键对水和衬底的相互作用的影响, Li和Zeng [2] 采用第一性原理分子动力学模拟观察了包含125个水分子的水滴分别悬浮在被固定住的石墨烯和h-BN表面, 并测量其浸润角. 关于第一性原理的精确度, 文献 [38]通过调节碳原子与SPCE模型水的相互作用, 获得了与实验值接近的接触角; 而Li 和Zeng [2] [40] 和电润湿的内容 [41] [2] Figure 1 (Color online) Snapshots of a water nanodroplet (125 water molecules) during the time evolution (in unit of ps) of the wetting process on a graphene sheet at 298 K (a), 385 K (b), and on the BN sheet at 385 K (c) [2] 时间较长, 是润湿溶解的主要成分. 而对于电溶解, 顾名思义即通过调节电压来控制界面液滴的状态.…”

Section: 纳米尺度下的润湿unclassified