Controlling Octagon-to-Square Wetting Interface Transition of Evaporating Sessile Droplet through Surfactant on Microtextured Surface

Zhong, Xin; Ren, Junheng; Chong, Karen S. L.; Ong, Kian Soo; Duan, Fei

doi:10.1021/acsami.8b02509

Cited by 14 publications

(19 citation statements)

References 23 publications

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“…Liquids in the Wenzel wetting state present a completely wetting solid-liquid contact area, desirable features for pesticide retention on plant surfaces 17 and boiling heat transfer 18 . Using highly enhanced capillarity and contact line pinning, spectacular properties of the Wenzel wetting state have been discovered, including directional and multilayer liquid spreading, as well as the formation of polygonal thin-liquid films and droplets 19 – 28 . For instance, Courbin et al 20 , 21 investigated deposited liquids on microtextured surfaces satisfying the imbibition condition and showed that they can form square, hexagonal, octagonal, and circular-shaped thin-liquid films.…”

Section: Introductionmentioning

confidence: 99%

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Polygonal non-wetting droplets on microtextured surfaces

Lou

Shi

et al. 2022

Nat Commun

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Understanding the interactions between liquids and solids is important for many areas of science and technology. Microtextured surfaces have been extensively studied in microfluidics, DNA technologies, and micro-manufacturing. For these applications, the ability to precisely control the shape, size and location of the liquid via textured surfaces is of particular importance for the design of fluidic-based systems. However, this has been passively realized in the wetting state thanks to the pinning of the contact line, leaving the non-wetting counterpart challenging due to the low liquid affinity. In this work, confinement is imposed on droplets located on well-designed shapes and arrangements of microtextured surfaces. An active way to shape non-wetting water and liquid metal droplets into various polygons ranging from triangles, squares, rectangles, to hexagons is developed. The results suggest that energy barriers in different directions account for the movement of the contact lines and the formation of polygonal shapes. By characterizing the curvature of the liquid-vapour meniscus, the morphology of the droplet is correlated to its volume, thickness, and contact angle. The developed liquid-based patterning strategy under active regulation with low adhesion looks promising for low-cost micromanufacturing technology, DNA microarrays, and digital lab-on-a-chip.

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Section: Introductionmentioning

confidence: 99%

“…The challenges lie in several aspects. First, liquid fronts can proceed spontaneously for complete and partial wetting cases 19 – 28 . However, thermodynamics suggests that capillary imbibition cannot take place on non-wetting surfaces 33 .…”

Section: Introductionmentioning

confidence: 99%

Polygonal non-wetting droplets on microtextured surfaces

Lou

Shi

et al. 2022

Nat Commun

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“…Very recent work (Zhong et al [16]) involved the addition of surfactants to control wetting geometry.…”

Section: ~√mentioning

confidence: 99%

Wetting phenomena observed in evaporating droplets on structured surfaces

Tekidou

Duursma

Mackenzie-Dover

et al. 2019

Heat Transfer Engineering

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A study was undertaken of ethanol droplet evaporation on structured surfaces of pillars (square pillars of variable dimensions and spacing of order microns, and cylindrical of various spacings). On seasoned perflourodecyltrichlorosilane surfaces, significant films were observed extending far beyond the initial contact line for pure ethanol droplets, most prominently for 4 microlitre droplets. On parylene coated surfaces, similar imbibed films were seen for 1.5 microlitre droplets of 50% by volume ethanol-water mixture. This film acts as an additional surface for evaporation and it appears that the droplet then serves as a reservoir for feeding the film until the evaporation process is completed, rather than evaporation being governed by evaporation at the contact line. The droplets with films show higher evaporation rates.

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“…Interestingly, compared with the study of ethanol droplets done by Feng et al, both KCl and ethanol produced the same effect on the shape of droplets, despite the different effect that these solutions have on surface tension. The study of droplet profile as a function of surfactant concentration on textured surfaces showed different wetting transitions of evaporating droplets, corresponding to the initial surfactant concentration [31,32] . The transition of droplet profile from octagon to square, and from square to rectangle, was observed during the drying process.…”

Section: Introductionmentioning

confidence: 99%

“…The transition of droplet profile from octagon to square, and from square to rectangle, was observed during the drying process. Additionally, the ability to maintain a uniform droplet profile throughout the whole evaporation process was achieved for octagonal droplets [31,32] . The findings unanimously demonstrate that surface chemistry and topography, as well as the intrinsic contact angle of the fluid, govern the wetting dynamics and droplet shape.…”

Section: Introductionmentioning

confidence: 99%

Geometrical Deposits on Microstructured Surfaces

et al. 2020

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Research into evaporating droplets on patterned surfaces has grown exponentially, since the capacity to control droplet morphology has proven to have significant technological utility in emerging areas of fundamental research and industrial applications. Here, we incorporate two interest domains-complex wetting patterns of droplets on structured surfaces and the ubiquitous coffee-ring phenomenon of nanofluids containing dispersed aluminium oxide particles. We lay out the surface design criteria by quantifying the effect of pillar density and shape on the wetting footprint of droplets, yielding complex polygon droplet geometries. Our work is not constrained to pure liquids only, as we delve into the shape selection of particle-laden droplets of different concentrations. We visualise the deposition patterns through microscopy on surfaces exhibiting different features and further establish the ordering of particles on microscale surface asperities. At a high nanofluid concentration, we observe intriguing self-assembly of particles into highly ordered intricate structures. The collective findings of this work have the potential to enhance many industrial technologies, particularly attractive for high performance optical and electrical devices.

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Controlling Octagon-to-Square Wetting Interface Transition of Evaporating Sessile Droplet through Surfactant on Microtextured Surface

Cited by 14 publications

References 23 publications

Polygonal non-wetting droplets on microtextured surfaces

Polygonal non-wetting droplets on microtextured surfaces

Wetting phenomena observed in evaporating droplets on structured surfaces

Geometrical Deposits on Microstructured Surfaces

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