Replicating and resolving wetting and adhesion characteristics of a Rose petal

Ghosh, Udita Uday; Nair, Sachin; Das, Anuja; Mukherjee, Rabibrata; DasGupta, Sunando

doi:10.1016/j.colsurfa.2018.10.028

Cited by 76 publications

(49 citation statements)

References 35 publications

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“…They mimicked the microstructure of the leave using soft lithography techniques and demonstrated an enhancement of 230% in water-harvesting on this surface. Ghosh et al 18 investigated wetting behavior and adhesion characteristics of a rose petal and resolved the liquid-substrate contact region using in-situ atomic force microscopy and confocal microscopy. They reported the Cassie impregnating wetting state on the rose petal, which does not let droplet to roll off from the surface.…”

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confidence: 99%

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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confidence: 99%

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

Kumar

Bhardwaj

2020

Sci Rep

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“…Pertinent question to ask at this point is why a water drop sticks on patterned ZnO NR array fabricated with larger d D . To answer this question, we draw the attention toward a recent paper by Ghosh et al, where the stickiness on a surface that is in Cassie state and entrapped air has been correlated to the curvature of the liquid–air interface over each pit . They attributed the stickiness on the negative replica of a rose petal to concave shape of the water meniscus over each pits.…”

Section: Resultsmentioning

confidence: 99%

“…Interestingly, none of these articles except the one by Gong et al could demonstrate sliding of a water drop on the ZnO covered surfaces, which is essential for achieving self‐cleaning behavior, despite exhibiting tremendously high θ*(>160°) in many cases. On the other hand, Li et al have shown that a dense ZnO NR array–covered surface exhibits sticky hydrophobicity, similar to that observed on a rose petal, which limits their practical application as superhydrophobic coatings. Afsal and Chen could even turn a fresh lotus leaf in to a sticky surface by growing a dense array of ZnO NR on it .…”

Section: Introductionmentioning

confidence: 96%

Colloidal Transfer Printing–Mediated Fabrication of Zinc Oxide Nanorods for Self‐Cleaning Applications

Banik

Chakrabarty

Das

et al. 2019

Adv Materials Inter

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Fabrication of superhydrophobic surfaces with extremely low contact angle hysteresis (θCAH < 4°), which exhibits excellent self‐cleaning behavior by colloidal template–guided hydrothermal growth of zinc oxide nanorods (ZnO NRs), is reported. A hexagonal close packed monolayer of polystyrene (PS) colloids is first deposited by spin coating on a thin poly(methyl methacrylate) (PMMA) film. Subsequently, the colloidal array is transferred to a substrate precoated with sputtered zinc oxide seed layer by UV‐Ozone (UVO) mediated colloidal transfer printing. ZnO NRs are grown with colloids of different diameter (dD) varying between 300 and 800 nm, and for each dD the growth time (tG) is optimized to obtain maximum level of hydrophobicity. These experiments show that best self‐cleaning property is achieved with colloids having dD = 600 nm and tG = 4 h, which do not require any subsequent low surface energy coating. Using transfer printing allows uniform coverage of the monolayer colloidal array over the sputtered seed layer spanning over large areas, irrespective of the roughness or curvature of the target substrate.

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“…Surfaces with controllable wetting properties are of great potential in downstream applications such as water harvesting, [ 1,2 ] self‐cleaning, [ 3–5 ] surface coating, [ 6,7 ] adhesion [ 8–10 ] and microfluidic devices. [ 11–14 ] One strategy to facilitate controllable surface wetting is to develop surface topographies, [ 15–17 ] thereby enabling a desired liquid/solid interaction.…”

Section: Figurementioning

confidence: 99%

Biaxially Morphing Droplet Shape by an Active Surface

Ding

Liu

Sridhar

et al. 2020

Adv Materials Inter

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Drop morphology can be manipulated by designing localized solid/liquid interactions to create a favorable interfacial energy equilibrium. A topographical surface with hierarchical roughness can be harnessed to generate complex drop morphologies, enhance uniaxial and anisotropic spreading, in a designable fashion. Here, using an active surface is proposed with a responsive roughness (wrinkle patterns) under uniaxial compression/stretching, to morph droplet shape biaxially in a continuous and reversible manner. The keys to achieve biaxial drop shaping are the in‐plane confinement from lattice hole patterns and the programmable formation of roughness, to pin and guide contact line movement in both in plane directions. The complex interplay between wetting and the patterns is elucidated by both experiments and numerical analysis. The results enrich the current understanding of shaping droplets by managing the contact line pinning/movement on an engineered elastic substrate, and providing insights for emerging applications in the areas such as droplet emicrofluidics, liquid robotics, ink‐jet printing, 3D printing and healthcare.

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Replicating and resolving wetting and adhesion characteristics of a Rose petal

Cited by 76 publications

References 35 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

Colloidal Transfer Printing–Mediated Fabrication of Zinc Oxide Nanorods for Self‐Cleaning Applications

Biaxially Morphing Droplet Shape by an Active Surface

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