Asymmetric temporal variation of oscillating AC electroosmosis with a steady pressure-driven flow

Hu, Zhongyan; Zhao, Tianyun; Wang, Hongxun; Zhao, Wei; Wang, Kaige; Bai, Jintao; Wang, Guiren

doi:10.1007/s00348-020-03060-z

Cited by 6 publications

(7 citation statements)

References 36 publications

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“…In contrast, the increasing Q tends to inhibit the nonlinear AC EOF, as can be found from the decreasingly nonsinusoidal and asymmetric time series of u ′* in Figure d–f. These findings are qualitatively consistent with previous investigations , and support that E A and Q are control parameters of AC EOF.…”

Section: Resultssupporting

confidence: 93%

“…Determining the universal control parameters for distinguishing different EOF statuses from linear to nonlinear is always a top priority for theoreticians and engineers who are seeking a practical strategy to utilize nonlinear EOF. Former investigation indicates the velocity fluctuations in an EOF driven by AC electric field are governed by an inviscid and general Burgers’ equation with forcing term ∂ u false′ false* ∂ t * + Z l ∂ u false′ false* ∂ x * + Z italicnl ∂ u false′ false* 2 ∂ x * = prefix− 2 π cos ( 2 π t * ) if a sinusoidal electric field is applied. The status of the flow field is determined by two dimensionless parameters, which are Z l = P e,U /StScγ 2 and Z nl = P e,EP /2StScγ 2 , where St = λ 2 ρ f f f /μ, Sc = μ/ρ f D , P e,EP = z 2 eE A L / k B T , and P e,U = UL / D are the Stokes number, Schmidt number, and Peclet numbers related to electrophoresis and local mean flow velocity, respectively.…”

Section: Resultsmentioning

confidence: 99%

Section: Table 1 Parameters In the Investigationmentioning

confidence: 99%

“…In the investigation, by an ultrasensitive nanoscopic velocity measurement technique, laser-induced fluorescent photobleaching anemometer (LIFPA), − we experimentally investigated the velocity fluctuation of an insulated wall driven by an AC electric field. Our purpose is to reveal the conditions corresponding to the very beginning of transitional AC EOF on the electrodes from linear to nonlinear state in a simple but fundamental model.…”

Section: Introductionmentioning

confidence: 99%

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Onset of Nonlinear Electroosmotic Flow under an AC Electric Field

Zhao

Chen

et al. 2022

Anal. Chem.

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Nonlinearity of electroosmotic flows (EOFs) is ubiquitous and plays a crucial role in ion transport, specimen mixing, electrochemistry reaction, and electric energy storage and utilization. When and how the transition from a linear regime to a nonlinear one occurs is essential for understanding, prohibiting, or utilizing nonlinear EOF. However, due to the lack of reliable experimental instruments with high spatial and temporal resolutions, the investigation of the onset of nonlinear EOF still remains in theory. Herein, we experimentally studied the velocity fluctuations of EOFs driven by an alternating current (AC) electric field via ultrasensitive fluorescent blinking tricks. The linear and nonlinear AC EOFs are successfully identified from both the time trace and energy spectra of velocity fluctuations. The transitional electric field (E A,C ) is determined by both the convection velocity (U) and AC frequency (f f ) as E A,C ∼ f f 0.48−0.027U . We hope the current investigation could be essential in the development of both theory and applications of nonlinear EOFs.

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Section: Resultssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Section: Table 1 Parameters In the Investigationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Onset of Nonlinear Electroosmotic Flow under an AC Electric Field

Zhao

Chen

et al. 2022

Anal. Chem.

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“…By establishing the monotonic relationship [5] between fluorescence intensity and flow velocity, the velocity of the flow field can be calculated by detecting the fluorescence signal intensity in the spot area [6]. This technique has been successfully applied to the velocity measurement of complex flow fields such as linearly and nonlinearly oscillating electroosmotic flow [7][8][9][10], and microelectrokinetic turbulence [11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of the Photobleaching Process in Laser-Induced Fluorescence Photobleaching Anemometer

et al. 2021

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At present, a novel flow diagnostic technique for micro/nanofluidics velocity measurement—laser-induced fluorescence photobleaching anemometer (LIFPA)—has been developed and successfully applied in broad areas, e.g., electrokinetic turbulence in micromixers and AC electroosmotic flow. Nevertheless, in previous investigations, to qualitatively reveal the dynamics of the photobleaching process of LIFPA, an approximation of uniform laser distribution was applied. This is different from the actual condition where the laser power density distribution is normally Gaussian. In this investigation, we numerically studied the photobleaching process of fluorescent dye in the laser focus region, according to the convection–diffusion reaction equation. The profiles of effective dye concentration and fluorescence were elucidated. The relationship between the commonly used photobleaching time constant obtained by experiments and the photochemical reaction coefficient is revealed. With the established model, we further discuss the effective spatial resolution of LIFPA and study the influence of the detection region of fluorescence on the performance of the LIFPA system. It is found that at sufficiently high excitation laser power density, LIFPA can even achieve a super-resolution that breaks the limit of optical diffraction. We hope the current investigation can reveal the photobleaching process of fluorescent dye under high laser power density illumination, to enhance our understanding of fluorescent dynamics and photochemistry and develop more powerful photobleaching-related flow diagnostic techniques.

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Simple Electroosmotic Pump and Active Microfluidics with Asymmetrically Coated Microelectrodes

et al. 2023

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Electroosmotic pumps can deliver liquid without moving parts, making them suitable for microfluidic and lab‐on‐chip systems. Previously, alternating current electroosmotic pumps were constructed using pairs of coplanar asymmetrical interdigitated microelectrodes on the same substrate. In this work, a simpler micropumping system is developed, separating the electrodes on two substrates and breaking the symmetry by half‐depositing electrodes with 3D microstructures. Numerical simulation models of the pumping system and experimental velocity profiles are used to explain the fluid motion mechanism and structure‐dependent pumping performance. In addition to its efficiency and simplicity, this new pumping system also allows for the creation of a microvortex device and an active microfluidics device. This scalable micropumping system provides a way to pump liquids at microscopic or macroscopical scale in complex microfluidics systems.

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Asymmetric temporal variation of oscillating AC electroosmosis with a steady pressure-driven flow

Cited by 6 publications

References 36 publications

Onset of Nonlinear Electroosmotic Flow under an AC Electric Field

Onset of Nonlinear Electroosmotic Flow under an AC Electric Field

Numerical Simulation of the Photobleaching Process in Laser-Induced Fluorescence Photobleaching Anemometer

Simple Electroosmotic Pump and Active Microfluidics with Asymmetrically Coated Microelectrodes

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