Droplet transportation using EWOD-induced wettability gradient

Yasuda, Takashi; Imamura, K.; Hirase, K.

doi:10.1109/sensor.2009.5285474

Cited by 6 publications

(2 citation statements)

References 7 publications

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“…Tuning of surface wettability using passive means, i.e., by surface texturing − and by active means, i.e., by external stimuli such as electrical forces, optical forces, magnetic forces, thermocapillary forces, surface acoustic waves, etc., has evoked significant interest due to its applications in digital microfluidics, lab-on-a-chip devices, droplet transportation,etc. − Among the above-mentioned external agents used to tune the wettability, electrical forces have drawn significant interest due to several advantages, like rapid movement of the droplet, higher maneuverability, choice of liquid, and higher change in wetting properties, thus making them more efficient in droplet actuation, dispensing, mixing, splitting, “lab-on-a-chip” devices, adjustable lenses, and display technology . Recently, several research groups have simultaneously used both passive and active means of tuning surface wettability by fabricating microstructured surfaces for electrowetting on dielectric (EWOD) − applications.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic Electrowetting on Wrinkled Surfaces: Enhanced Wetting and Dependency on Initial Wetting State

et al. 2018

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Electrowetting on dielectric (EWOD) on unidirectional microstructured surfaces has recently evoked significant interest as they can modulate the effect of electrowetting, and can thus find applications in directional wetting in microfluidic systems. However, the dependency of such EW phenomenon on their initial state of wetting and anisotropy is far from being well understood. The current study addresses the initial wetting states and their implication on the anisotropic electrowetting using a wrinkled EWOD platform. Herein we demonstrate a facile stampless and maskless structure generation technique to fabricate wrinkles of varying topography. Further, we have demonstrated alteration in the interfacial wetting conditions by modulating the wrinkle topography, and its effect on the droplet behavior during electrowetting. The capillary wicking-assisted electrowetting on these wrinkled surfaces is in specific direction dictated by the ordered wrinkles and prompts enhanced spreading of the droplet. We also demonstrate that while the enhancement of unidirectional electrowetting is stronger in conformal wetting state surfaces, composite wetting state surfaces depict a reversal in anisotropy.

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Section: Introductionmentioning

confidence: 99%

Anisotropic Electrowetting on Wrinkled Surfaces: Enhanced Wetting and Dependency on Initial Wetting State

et al. 2018

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“…But the transporting distances of the stripe-patterned and circle-patterned gradient surfaces are small. Wedge-shaped surfaces can offer continuous gradients for droplet transport [29]. Khoo et al achieved spontaneous high-speed transport of droplet on wedge-shaped nanotextured surfaces [30].…”

Section: Introductionmentioning

confidence: 99%

Patterned gradient surface for spontaneous droplet transportation and water collection: simulation and experiment

Tan

Zhu

Shi

et al. 2016

J. Micromech. Microeng.

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We demonstrate spontaneous droplet transportation and water collection on wedge-shaped gradient surfaces consisting of alternating hydrophilic and hydrophobic regions. Droplets on the surfaces are modeled and simulated to analyze the Gibbs free energy and free energy gradient distributions. Big half-apex angle and great wettability difference result in considerable free energy gradient, corresponding to large driving force for spontaneous droplet transportation, thus causing the droplets to move towards the open end of the wedge-shaped hydrophilic regions, where the Gibbs free energy is low. Gradient surfaces are then fabricated and tested. Filmwise condensation begins on the hydrophilic regions, forming wedge-shaped tracks for water collection. Dropwise condensation occurs on the hydrophobic regions, where the droplet size distribution and departure diameters are controlled by the width of the regions. Condensate water from both the hydrophilic and hydrophobic regions are collected directionally to the open end of the wedge-shaped hydrophilic regions, agreeing with the simulations. Directional droplet transport and controllable departure diameters make the branched gradient surfaces more efficient than smooth surfaces for water collection, which proves that gradient surfaces are potential in water collection, microfluidic devices, anti-fogging and self-cleaning.

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Large‐Range, Reversible Directional Spreading of Droplet on a Double‐Gradient Wrinkled Surface Adjusted Under Mechanical Strain

Chai

Tian

et al. 2020

Adv Materials Inter

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Dynamical regulation to unidirectional wetting has received considerable attention in recent years due to its important role in flexible electronics, microfluidics, drug transportation, and so forth. It is of great significance to prepare a surface which allows the droplet to spread directionally on it with the length of droplet reversibly fluctuated within a broad range under external stimulation. In this paper, a double‐gradient wrinkled structure is prepared by constructing the structure‐gradient pillar arrays on a mechanics‐adjusted wrinkled surface and subsequently making chemical gradient by oxygen plasma treatment. Under the synergistic effect of the structural gradient, chemical gradient, and wrinkled structure, the droplet can undergo unidirectional spreading and realize dynamic regulation of the spreading length on the flexible structure. This will provide a propagable method for the regulation of surface wetting.

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Droplet transportation using EWOD-induced wettability gradient

Cited by 6 publications

References 7 publications

Anisotropic Electrowetting on Wrinkled Surfaces: Enhanced Wetting and Dependency on Initial Wetting State

Anisotropic Electrowetting on Wrinkled Surfaces: Enhanced Wetting and Dependency on Initial Wetting State

Patterned gradient surface for spontaneous droplet transportation and water collection: simulation and experiment

Large‐Range, Reversible Directional Spreading of Droplet on a Double‐Gradient Wrinkled Surface Adjusted Under Mechanical Strain

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