Dissipative Particle Dynamics Simulation of Droplet Oscillations in AC Electrowetting

Li, Zhen; Zhe-wei, Zhou; Hu, Guohui

doi:10.1163/156856111x600217

Cited by 11 publications

(5 citation statements)

References 29 publications

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“…The results correspond to three representative time instants in the P 2 , P 4 and P 6 oscillation modes (Note: 1) the initial time instant, t = 0 ms, was chosen somewhat arbitrarily, and 2) the images shown were for the descending half-cycle of the droplet movement). It is interesting to notice that the velocity vector field is in very good agreement with the numerical results obtained in [32,34]. Furthermore, recirculation swirls can be identified from the streamline contours, and the number of vortices matches the respective resonance modes.…”

Section: Droplet Dynamics In Acewsupporting

confidence: 83%

“…(1) to acquire the time-averaged contact angle at different actuating frequencies. In a study of droplet dynamics in ACEW, Li et al [34] followed the electrical wetting tension concept but used a dissipative particle dynamics (DPD) approach, which is a modified version of the lattice gas method by replacing single fluid molecules with coarse-grained particle clusters. Unfortunately, only the oscillations of a sub-micrometer droplet in ACEW were explored due to the computational limits of the DPD approach.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Dynamics of droplet motion induced by Electrowetting

Sur

Pascente

et al. 2017

International Journal of Heat and Mass Transfer

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Electrowetting (EW) has drawn significant interests due to the potential applications in electronic displays, lab-on-a-chip microfluidic devices and electro-optical switches, etc. However, current understanding of EW is hindered by the inadequacy of available numerical and theoretical methods in properly modeling the transient behaviors of EW-actuated droplets. In the present work, a combined numerical and experimental approach was employed to study the EW response of a droplet subject to both direct current (DC) and alternating current (AC) actuating signals. Computational fluid dynamics models were developed by using the Volume of Fluid (VOF)-Continuous Surface Force (CSF) method. A dynamic contact angle model based on the molecular kinetic theory was implemented as the boundary condition at the moving contact line, which considers the effects of the contact line friction and the pinning force. The droplet shape evolution under DC condition and the interfacial resonance oscillation under AC condition were investigated. It was found that the numerical models were able to accurately predict the key parameters of electrowetting-induced droplet dynamics.

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Section: Droplet Dynamics In Acewsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Dynamics of droplet motion induced by Electrowetting

Sur

Pascente

et al. 2017

International Journal of Heat and Mass Transfer

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“…Ever since its inception, the mDPD model has been successfully applied to investigations of diverse wetting phenomena and multiphase flows. Examples include the two phase flows in a Y-shaped channel [45], manipulation of liquid droplets using wetting gradient [46] and electrowetting [47], dynamics of droplets sliding across micropillars [48] and impacting on textured surfaces [49], and multiphase flows through nanoporous shales [50], to name but a few.…”

Section: Many-body Dpd Modelmentioning

confidence: 99%

Self-Cleaning of Hydrophobic Rough Surfaces by Coalescence-Induced Wetting Transition

et al. 2019

Self Cite

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The superhydrophobic leaves of a lotus plant and other natural surfaces with self-cleaning function have been studied intensively for the development of artificial biomimetic surfaces. Surface roughness generated by hierarchical structures is a crucial property required for superhydrophobicity and self-cleaning. Here, we demonstrate a novel self-cleaning mechanism of textured surfaces attributed to a spontaneous coalescence-induced wetting transition. We focus on the wetting transition as it represents a new mechanism, which can explain why droplets on rough surfaces are able to change from the highly adhesive Wenzel state to the low-adhesion Cassie-Baxter state and achieve self-cleaning. In particular, we perform many-body dissipative particle dynamics simulations of liquid droplets (with diameter 89 µm) sitting on mechanically textured substrates. We quantitatively investigate the wetting behavior of an isolated droplet as well as coalescence of droplets for both Cassie-Baxter and Wenzel states. Our simulation results reveal that droplets in the Cassie-Baxter state have much lower contact angle hysteresis and smaller hydrodynamic resistance than droplets in the Wenzel state. When small neighboring droplets coalesce into bigger ones on textured hydrophobic substrates, we observe a spontaneous wetting transition from a Wenzel state to a Cassie-Baxter state, which is powered by the surface energy released upon coalescence of the droplets. For superhydrophobic surfaces, the released surface energy may be sufficient to cause a jumping motion of droplets off the surface, in which case adding one more droplet to coalescence may increase the jumping velocity by one order of magnitude. When multiple droplets are involved, we find that the spatial distribution of liquid components in the coalesced droplet can be controlled by properly designing the overall arrangement of droplets and the distance between them. These findings offer new insights for designing effective biomimetic self-cleaning surfaces by enhancing spontaneous Wenzel-to-Cassie wetting transitions, and additionally, for developing new non-contact methods to manipulate liquids inside small droplets via multiple-droplet coalescence.

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“…The pressure of the system be-comes a cubic relationship with density, which can generate a free interface. This many-body dissipative particle dynamics method has been widely used to simulate droplet dynamics on substrates, multiphase flow in complex geometry and phase transition problems [10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Temperature-dependent properties of liquid-vapour coexistence system with many-body dissipative particle dynamics with energy conservation

Zhang,

Li,

Chen

et al. 2020

Preprint

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The dynamic properties of fluid, including density, surface tension, diffusivity and viscosity, are temperaturedependent and can significantly influence the flow dynamics of mesoscopic non-isothermal systems. To capture the correct temperature-dependence of a fluid, a many-body dissipative particle dynamics model with energy conservation (mDPDe) is developed by combining the temperature-dependent coefficient of the conservative force and weighting terms of the dissipative and random forces. The momentum and thermal diffusivity, viscosity, and surface tension of liquid water at various temperatures ranging from 273 K to 373 K are used as examples for verifying the proposed model. Simulations of a periodic Poiseuille flow driven by body forces and heat sources are carried out to validate the diffusivity of the present model. Also, a steady case of heat conduction for reproducing the Fourier law is used to validate the thermal boundary conditions. By using this mDPDe simulations, the thermocapillary motion of liquid water nanodroplets on hydrophobic substrates with thermal gradients is investigated. The migration of the droplet is observed on flat substrates with gradient temperature. The velocity of the migration becomes larger for higher temperature difference, which is in agreement with the present theoretical analysis and DVDWT simulations. The results illustrate that the modified model can be used to study Marangoni effect on a nanodroplet and other heat and mass transfer problems with free interface.

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Dissipative Particle Dynamics Simulation of Droplet Oscillations in AC Electrowetting

Cited by 11 publications

References 29 publications

Dynamics of droplet motion induced by Electrowetting

Dynamics of droplet motion induced by Electrowetting

Self-Cleaning of Hydrophobic Rough Surfaces by Coalescence-Induced Wetting Transition

Temperature-dependent properties of liquid-vapour coexistence system with many-body dissipative particle dynamics with energy conservation

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