The effect of sharp solid edges on the droplet wettability

Wang, Zhanlong; Lin, Kui; Zhao, Ya‐Pu

doi:10.1016/j.jcis.2019.05.081

Cited by 52 publications

(29 citation statements)

References 55 publications

(75 reference statements)

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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: 82%

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: 82%

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

Kumar

Bhardwaj

2020

Sci Rep

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“…The pinning force reaches a maximum at the depinning moment and is always in the opposite direction of the movement trend of the liquid. [ 22,50,51 ] When the liquid tends to squeeze into the microcavity, due to the strong edge effect of the small microsize of microcavity, the meniscus of wetting liquid at the entrance of microcavity vertically sagged at the initial pinning stage (Figure 4d). [ 41 ] Other researchers also found that even hydrophilic surfaces showed hydrophobicity near the edge of microcavity.…”

Section: Resultsmentioning

confidence: 99%

Directional Metastable Wetting Evolution of Droplets on Artificial Patterned Microcavity Surfaces

Liu

Xiao

et al. 2021

Adv Materials Inter

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Controllable wetting transition on artificial microtextured surfaces has significant applications in many industrial fields. In this work, the droplet spreading and the directional wetting transition are investigated on the substrate surface with the patterned microcavities. The results show that the macroscopic inward wetting transition from the periphery to the center of the droplet strongly depends on the mesoscopic sequential transition from Cassie to Wenzel state in the microcavities on the substrate surfaces. The semiquantitative relationship between sagging depth of meniscus in the microcavities and the droplet spreading velocity is set up by utilizing scaling‐law analysis in terms of mechanical equilibrium of the meniscus. This finding is expected to help to clarify the issues on the mechanism and main affecting factors of the wetting transition on the patterned surface.

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“…On the surface of a solid metal, such as a smooth zinc block, the chemical reactions result in a rough surface morphology, for example, sharp roughness or defects. These defects can severely impede droplet movement; [ 32 ] a droplet on these surfaces generally stands still.…”

Section: Figurementioning

confidence: 99%

Realization of Self‐Rotating Droplets Based on Liquid Metal

Wang

Miao

et al. 2020

Adv Materials Inter

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Owing to their fascinating characteristics, liquid metals (LMs) have attracted increasing attention from the scientific community, and are a potential material for various applications. A novel phenomenon is reported in which an acid droplet spontaneously rotates on the surface of an LM. The experimental results show that this phenomenon originates from the collective motion of bubbles generated by the chemical reactions between the droplet and the LM. The angular velocity of the droplet rotation is on the order of 101 rad s−1, which is much higher than that driven by other mechanisms. Under different conditions, the period of the droplet differs, and it increases with the pH and radius of the acid droplet. The theoretical results indicate the dominant factors and the characterized angular velocity, which agree well with the experimental data. This phenomenon demonstrate that the general particles can also induce special spatial–temporal patterns, and opens up a new field for the application of LMs.

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The effect of sharp solid edges on the droplet wettability

Cited by 52 publications

References 55 publications

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

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

Directional Metastable Wetting Evolution of Droplets on Artificial Patterned Microcavity Surfaces

Realization of Self‐Rotating Droplets Based on Liquid Metal

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