Reducing the droplet/solid interfacial sliding resistance under electrowetting-on-dielectric by different voltage slew rate signals

Zhang, Yafeng; Wang, Yongning; Tang, Cheng Chun; Zhou, Guiyuan; Yu, Jiaxin; He, Hongtu; Qi, Huiming

doi:10.1016/j.colsurfa.2020.125075

Cited by 5 publications

(5 citation statements)

References 35 publications

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“…where C D , A D , ρ f and U denote the drag coefficient, projected area, air density and droplet velocity, respectively. [13] According to the observation of Oprins et al, [22] it is found that when air is the filling medium the resistance can be ignored. The imbalance of electric field force and friction force will cause acceleration on the contact line.…”

Section: Dynamic Contact Angle Modelmentioning

confidence: 99%

“…The amplitude and frequency of the droplet oscillation change differently with the surface wettability in different phase regimes. Ko et al [13] observed hydrodynamic flow in droplets using an AC voltage from a configuration with air as the ambient phase. The flow was observed using a laser sheet and fluorescent tracers, and a toroidal vortex flow was reported.…”

Section: Introductionmentioning

confidence: 99%

“…The effects of droplet physical characteristics, [17] electric field magnitude, [17,18] polarity [10,14] and wall hydrophobicity [12,13] on the electrowet-ting phenomenon under DC or AC electric fields have been extensively studied. However, the internal flow field mechanism of droplets under alternating current electrowetting (ACEW), as well as the effects of voltage frequency and initial phase angle on the dynamic contact behavior of droplets, have not been thoroughly and completely investigated.…”

Section: Introductionmentioning

confidence: 99%

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Transient study of droplet oscillation characteristics driven by an electric field

Gao

Abdalazeem

et al. 2023

Chinese Phys. B

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Electrowetting technology, one of the microfluidic technologies, has attracted more and more attentions in recent years, and it has a broad prospect in terms of microdroplet drive. In this paper, the dynamic contact angle theory is used to develop a numerical model to predict the droplet dynamic contact behavior and the internal flow field under electrowetting. In particular, based on the established computational model of droplet force balance, the dynamic process of a droplet under electrowetting is analyzed, with the perspective of pressure variation and force balance inside the droplet. The results show that when the alternating current frequency increases from 50Hz to 500Hz, the amplitude of the oscillation waveform after droplet stabilization is 0.036mm, 0.016mm, 0.013mm, 0.002mm, while the relevant droplet oscillation periods T are 11ms, 4ms, 2ms, 1ms, respectively. It is also found that the initial phase angle does not affect the droplet oscillation amplitude. In addition, the pressure on the droplet surface under alternating current electrowetting increases rapidly to the maximum value, with resonant waveform oscillation, and the droplet will present different resonance modes under voltage stimulation. The higher the resonance mode is, the smaller the droplet oscillation amplitude is, and the streamline at the interface will present eddy current, in which the number of vortices matches the resonance mode. The high resonance mode corresponds to the small droplet amplitude, while there are more vortices with smaller size.

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Section: Dynamic Contact Angle Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Transient study of droplet oscillation characteristics driven by an electric field

Gao

Abdalazeem

et al. 2023

Chinese Phys. B

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“…One common way is to prestretch the droplet on the substrate using traditional EW. By suddenly releasing the electric voltage, the droplet recoils on the solid surface. ,− Dewetting is induced by the stored energy in the prestretched surface while in the whole process, the droplet is in contact with the inserted needle electrode. Recently, Edwards et al considered the dielectrowetting effect and induced droplet dewetting in a noncontactable manner, that is, by embedding a linear stripe array of interdigitated electrodes in the glass substrate.…”

Section: Introductionmentioning

confidence: 99%

“…Once dewetting completely, the droplet will detach from the hostile surface. In EW, droplet detachment was induced generally by the passive method as mentioned above, for example, by prestretching the interface and releasing the droplet to recoil and jump. − However, the operating condition is quite strict. Experiments showed that a variety of factors influence the EW-induced detachment, such as external voltage, fluid viscosity, surface wettability, droplet volume, and so forth. ,, Vo and Tran investigated the critical conditions for jumping droplets in EW and established a criterion equation by taking account of contact line dissipation, pinning effect, droplet elasticity, and surface energy.…”

Section: Introductionmentioning

confidence: 99%

Manipulation of a Nonconductive Droplet in an Aqueous Fluid with AC Electric Fields: Droplet Dewetting, Oscillation, and Detachment

Wang

et al. 2021

Langmuir

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Electrowetting (EW) is an effective method for droplet manipulation in microfluidics. In traditional EW, a conductive droplet is actuated, which spreads on a solid substrate. Recently, we considered an opposite phenomenon of droplet actuation in EW: inducing nonconductive droplet dewetting and detaching from the substrate. An oil/water system is used in which the oil droplet (nonconductive) is actuated on a flat substrate in surrounding water (conductive) by EW. In this work, alternating current (AC) electric fields are applied to EW, and the transient dynamics of droplet dewetting, oscillation, and detachment with the AC signals are investigated. The droplet is not in contact with electrodes, and it dances freely on the substrate. Experiments are performed in a wide range of voltages and AC frequencies. To demonstrate the droplet dynamics, we divide the full process of droplet manipulation into three distinguishable periods, that is, an initiating period, a steady oscillation period, and a detaching condition. Transient droplet dewetting is considered in the initiating period, and we obtain the distribution of the contact line friction factor. In steady oscillation, the oscillation resonance is verified from the oscillating amplitude of the contact line. Different periodical features are found for the droplet dancing at the resonance frequencies and departure from resonance. The droplet is detached at high voltages, and we provide a map for the detachable and nondetachable zones. The voltage is the dominant factor determining the droplet detachment; however, the AC frequency has notable influences on the critical voltage. The detachment is promoted when the AC frequency is within the region of the oscillation resonance (e.g., 20 < f < 75 Hz). In this region, the detaching process is not monotonic but instead, the droplet rebounds by several times before it is completely detached.

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Study on the adhesion behaviors between droplet and polydimethylsiloxane film

Dong

Zhang

et al. 2021

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Reducing the droplet/solid interfacial sliding resistance under electrowetting-on-dielectric by different voltage slew rate signals

Cited by 5 publications

References 35 publications

Transient study of droplet oscillation characteristics driven by an electric field

Transient study of droplet oscillation characteristics driven by an electric field

Manipulation of a Nonconductive Droplet in an Aqueous Fluid with AC Electric Fields: Droplet Dewetting, Oscillation, and Detachment

Study on the adhesion behaviors between droplet and polydimethylsiloxane film

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