Sessile drop response to a single wave electrokinetic excitation

Quintero, Juan Sebastian Marin; Waghmare, Prashant R.

doi:10.1063/5.0026878

Cited by 8 publications

(8 citation statements)

References 72 publications

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“…The viscous dissipation, spreading momentum caused by external triggering, and interfacial energies dictate the oscillatory behavior. We have studied this oscillation-damping effect in our previous paper . The change in the magnitude of the bridge height and the frequency of oscillatory motion is associated with the underdamped regime, in which the drop oscillates and the magnitude of these oscillations decay exponentially over time , until steady state is reached.…”

Section: Resultsmentioning

confidence: 99%

“…The drops consisted of aqueous solutions of glycerol and 0.1 M sodium chloride. The properties of the liquids used as the droplet and surrounding medium at room temperature are presented in Table I in the Supporting Information . Charges at the bottom copper substrate, and the ions and their associated charges, which are generated on the dielectric substrate and droplet interfaces when the electric field is applied to aqueous droplets is illustrated in Figure (a)(ii)).…”

Section: Methodsmentioning

confidence: 99%

“…The properties of the liquids used as the droplet and surrounding medium at room temperature are presented in Table I in the Supporting Information. 28 Charges at the bottom copper substrate, and the ions and their associated charges, which are generated on the dielectric substrate and droplet interfaces when the electric field is applied to aqueous droplets is illustrated in Figure 1(a)(ii)). When the electric field is applied, due to the electrostatic force, droplets spread over the dielectric substrate, followed by coalescence (see Figure 1(a)(iii)).…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

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Electrowetting-Induced Coalescence of Sessile Droplets in Viscous Medium

et al. 2023

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Manipulating the coalescence of microdroplets has recently gained enormous attention in digital microfluidics and biological and chemical industries. Here, coalescence between two sessile droplets is induced by spreading them due to electrowetting. The electrocoalescence dynamics is investigated for a wide range of operating parameters such as electrowetting number, Ohnesorge number, driving frequency, and drop to surrounding medium viscosity ratio. Here, the characteristic time scale from the classical lubrication theory is modified with an additional driving and resisting force due to the electrostatic pressure force and liquid–liquid viscous dissipation, respectively. With the revised characteristic time scale, a universal bridge growth is shown between the two merging droplets following a 1/3 power law during early coalescence followed by a long-range linear variation. To ensure precise control on droplet coalescence, a geometric analysis is also performed to define the initial separation distance.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: ■ Experimental Sectionmentioning

confidence: 99%

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Electrowetting-Induced Coalescence of Sessile Droplets in Viscous Medium

et al. 2023

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“…Drop oscillation dynamics on a thin liquid film is related to many natural applications such as in enhancing condensation, − water harvesting, − liquid infused surfaces (LIS), − and drop impact dynamics. − In particular, recent studies have shown that drop oscillation, induced by surface vibrations, enhances the mobility of sessile drops − and the pinching dynamics of pendant drops. − When the forcing frequencies match the natural frequencies of the drops, the oscillation reaches a resonant state, maximizing the excitation amplitude. − The high amplitude at the resonant state leads to longitudinal or lateral drop motion, generating contact line movement. Yao et al showed that oscillating drops at the first resonant frequency, as opposed to the second resonant frequency, allowed for drops to overcome contact angle hysteresis and enhanced drop mobility .…”

Section: Introductionmentioning

confidence: 99%

Oscillation Dynamics of Drops on Immiscible Thin Liquid Films

Tran

Sakakeeny

et al. 2022

Langmuir

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While drop oscillation dynamics has been widely studied for many decades, the influence of a moving contact line on the oscillation modes of drops remains underexplored. Herein, we report the oscillation dynamics of drops on thin liquid films with different viscosities where lower viscosities provide a slipping surface and higher viscosities immobilize the contact line. A gently deposited drop onto an oil film undergoes shape oscillations due to capillarity, where the frequency, amplitude, and apparent contact angle are tracked via a high-speed camera. This study demonstrates that restraining the mobility of the drop contact line by increasing the viscosity of a thin oil film underneath the drop increases the extent of the drop oscillation time as well as affecting the natural frequency of the drop oscillation. The drop oscillation time was defined by the time at which the changes in the drop height dropped to values less than 1% of the equilibrium height. The experimental results for the first longitudinal mode oscillation frequencies as a function of the equilibrium contact angles for the pinning and slipping contact lines were in good agreement with previously reported numerical simulations and model predictions.

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“…For example, the liquid viscosity is an important parameter affecting the performance of EWOD-based liquid handling. Marin Quintero and Waghmare 43 found that the deformation response of sessile droplets in EWOD is affected by both the system viscosity and the electrical signal parameters. However, the effects of liquid viscosity on the formation, propagation, and attenuation of EWCWs have not yet been reported.…”

Section: ■ Introductionmentioning

confidence: 99%

Effects of Liquid Viscosity on the Formation and Attenuation of Capillary Waves Induced by AC Electrowetting-on-Dielectric

et al. 2022

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The capillary waves induced by electrowetting-ondielectric have great potential in terms of capillary propulsion and other applications. At present, these applications are limited by a lack of research on the effects of liquid viscosity, which is an important parameter in controlling this phenomenon. This paper examines the formation, propagation, and attenuation of electrowetting-on-dielectric-induced capillary waves (EWCWs) on a liquid-free surface with different levels of liquid viscosity. The formation and propagation of the capillary waves are visualized using a high-speed camera and a free-surface synthetic Schlieren method. A theoretical model is established to describe the wave amplitude and wave propagation of EWCWs. The results show that the liquid viscosity, as well as the surface tension, significantly affects the formation and propagation of EWCWs. Using the results presented in this paper, a new type of Stokes viscometer based on EWCWs is proposed, enabling accurate measurements of liquid viscosity over a wide range of viscosity and temperature conditions.

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Sessile drop response to a single wave electrokinetic excitation

Cited by 8 publications

References 72 publications

Electrowetting-Induced Coalescence of Sessile Droplets in Viscous Medium

Electrowetting-Induced Coalescence of Sessile Droplets in Viscous Medium

Oscillation Dynamics of Drops on Immiscible Thin Liquid Films

Effects of Liquid Viscosity on the Formation and Attenuation of Capillary Waves Induced by AC Electrowetting-on-Dielectric

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