Rapid mixing with high‐throughput in a semi‐active semi‐passive micromixer

Kunti, Golak; Bhattacharya, Anandaroop

doi:10.1002/elps.201600393

Cited by 72 publications

(48 citation statements)

References 39 publications

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“…Thus, as a leading role electrothermal forces generate the circulations in the droplets and promote efficient mixing ability. Such electrothermal motion were applied in the operations of fluid pumping , mixing of analytes , controlling two‐phase flow , and particle manipulation . Based on the above description of the governing equations, we have performed numerical simulation to understand the flow field and thermal field.…”

Section: Methodsmentioning

confidence: 99%

Strong rotating flow in stationary droplets in low power budget using wire electrode configuration

2019

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We explore a simple strategy of generating strong rotating flow in a stationary surface‐droplet, using an intricate interplay of local electrical and thermal fields. Wire electrodes are employed to generate on‐spot heating without necessitating any elaborate micro‐fabrication, which causes strong local gradients in electrical properties to induce mobile charges into the droplet. Applying a low voltage (∼10 V), strong rotational velocity of the order of mm/s can be achieved in the system, within the standard operating ranges of operating and geometrical parameters. Further, altering the diameter of the electrode, vortices can be tuned locally or globally in low power budget, without incurring any droplet oscillations. These results may turn out to be of immense consequence in enhancing micromixing in a plethora of droplet based applications ranging from thermal management to medical diagnostics to be potentially employed in resource‐limited settings.

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Section: Methodsmentioning

confidence: 99%

Strong rotating flow in stationary droplets in low power budget using wire electrode configuration

2019

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“…These limitations notwithstanding, local fluid recirculation can also be generated thermally via other means, for example, via the photoacoustic effect discussed previously in Section . Alternatively, local Joule heating as a consequence of the applied electric field, or externally imposed, for example using a laser, can give rise to temperature gradients in the fluid, that can also result in nonuniform permittivity ε and conductivity σ, and hence an accumulation of space charge ρ e that manifests as a time‐averaged (for AC fields) Maxwell body force

(⟨⟩, F_{e}) = \frac{1}{2} Re ([], \frac{σ ε}{σ + normali ω ε} \{\frac{1}{ε} (\frac{\partial ε}{\partial T}) - \frac{1}{σ} (\frac{\partial σ}{\partial T})\} (\nabla T \cdot E) E^{*} - \frac{1}{2} \frac{\partial ε}{\partial T} {|E|}^{2} \nabla T)

in a phenomena known as the electrothermal effect. In the above, σ is the conductivity of the fluid, T the temperature and E the electric field, the asterisk * denoting its complex conjugate and Re[·] the real part of the term in the parenthesis.…”

Section: Active Actuationmentioning

confidence: 99%

On‐Chip Generation of Vortical Flows for Microfluidic Centrifugation

Ahmed

Ramesan

Lee

et al. 2019

Small

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Microcentrifugation constitutes an important part of the microfluidic toolkit in a similar way that centrifugation is crucial to many macroscopic procedures, given that micromixing, sample preconcentration, particle separation, component fractionation, and cell agglomeration are essential operations in small scale processes. Yet, the dominance of capillary and viscous effects, which typically tend to retard flow, over inertial and gravitational forces, which are often useful for actuating flows and hence centrifugation, at microscopic scales makes it difficult to generate rotational flows at these dimensions, let alone with sufficient vorticity to support efficient mixing, separation, concentration, or aggregation. Herein, the various technologies—both passive and active—that have been developed to date for vortex generation in microfluidic devices are reviewed. Various advantages or limitations associated with each are outlined, in addition to highlighting the challenges that need to be overcome for their incorporation into integrated microfluidic devices.

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“…In order to estimate the mixing efficiency, we calculated the mean concentration

0true C_{m e a n} (x) = \sum_{i = 1}^{n} C (x, y, z) / n

and the concentration SD

C_{sd} false(x false) = \sqrt{0true \sum_{i = 1}^{n} {false[C (x, y, z) - C_{mean} (x) false]}^{2} / (n - 1)}

on circular transverse cross‐section at a given x‐position. The index of mixing efficiency

0true γ (x) = (1 - \int \int_{normalS} | C - C_{\infty} | d_{y} d_{z} / \int \int_{normalS} | C_{0} - C_{\infty} | d_{y} d_{z}) \times 100 %

used in most of the literatures was not employed in this study because of the undeterminable completely mixer state

C_{\infty}

. The degree of concentration divergence represented by mean and SD of concentration can describe the mixing efficiency availably herein.…”

Section: Theory and Simulationmentioning

confidence: 99%

“…100% used in most of the literatures [25,26] was not employed in this study because of the undeterminable completely mixer state C ∞ . The degree of concentration divergence represented by mean and SD of concentration can describe the mixing efficiency availably herein.…”

Section: Theory and Simulationmentioning

confidence: 99%

“…However, the ACET effect can generate vortices in the bulk of a fluid by ACEK forces, and eventually can stir the flow to enhance the mixing. The ACET effect has been used to effectively enhance the performance of heterogeneous immunoassays in microfluidic systems in experiments and numerical studies [23][24][25]. These results show that the response time, sensitivity, and binding efficiency can be reliably improved by electrothermal stirring.…”

mentioning

confidence: 99%

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Biofluid pumping and mixing by an AC electrothermal micropump embedded with a spiral microelectrode pair in a cylindrical microchannel

Gao

2018

Electrophoresis

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In this paper, we numerically investigated a multifunctional AC electrothermal (ACET) micropump embedded with an asymmetric spiral microelectrode pair in a cylindrical microchannel for simultaneous pumping and mixing in high‐conductivity fluids, which makes the pump useful for biofluid applications. When an AC signal was applied to the asymmetric spiral electrode pair, the vortices induced on the electrode surfaces with centerlines along the corresponding spiral electrode length exhibit a spiral distribution, and the net flow in the cylindrical microchannel is generated by the ACET effect. The vorticity field distribution can explain the mechanism of simultaneous pumping and mixing. Because the vorticity field is inclined against the microchannel direction, vortices on top of the spiral electrodes can affect the ACET flow in the following two aspects at the same time: one is pumping the flow in the microchannel direction, and the other is mixing the samples by stirring the flow. We also determined that the geometric ratios of the electrode width to the gap or slant angle of the spiral electrodes can feasibly be used to control the relative strength of the pumping and mixing capabilities, and we achieved an optimal design that gives both desirable pumping and mixing efficiencies. This study shows that the spiral ACET micropump design can rapidly drive the high‐conductivity fluids and efficiently mix samples simultaneously. The numerical simulation of the spiral ACET micropump is of significant importance for practical, chemical and biological applications, and feasible fabrication techiniques should be experimentally investigated in future studies.

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Rapid mixing with high‐throughput in a semi‐active semi‐passive micromixer

Cited by 72 publications

References 39 publications

Strong rotating flow in stationary droplets in low power budget using wire electrode configuration

Strong rotating flow in stationary droplets in low power budget using wire electrode configuration

On‐Chip Generation of Vortical Flows for Microfluidic Centrifugation

Biofluid pumping and mixing by an AC electrothermal micropump embedded with a spiral microelectrode pair in a cylindrical microchannel

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