Energy-efficient generation of controlled vortices on low-voltage digital microfluidic platform

Kunti, Golak; Dhar, Jayabrata; Bandyopadhyay, Saumyadwip; Bhattacharya, Anandaroop; Bhattacharjee, Anirban

doi:10.1063/1.5042143

Cited by 11 publications

(11 citation statements)

References 20 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%

“…• AC electroosmotic flow -Capacitive charging [67][68][69][70] -Faradaic charging [68,71,72] Electrothermal effect [73][74][75][76][77][78][79][80][81][82] Interfacial electrokinetics…”

Section: Active Actuation Mechanismsmentioning

confidence: 99%

“…These limitations notwithstanding, local fluid recirculation can also be generated thermally via other means, for example, via the photoacoustic effect discussed previously in Section 3.2. Alternatively, local Joule heating as a consequence of the applied electric field, [73][74][75][76] or externally imposed, for example using a laser, [77][78][79] 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 [226] 1 2…”

Section: Thermal Actuationmentioning

confidence: 99%

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On‐Chip Generation of Vortical Flows for Microfluidic Centrifugation

Ahmed

Ramesan

Lee

et al. 2019

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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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“…[19][20][21][22][23][24] Alternating current electrokinetics (ACEK) stands as an effective choice for manipulating fluid flows in several devices of these kinds, considering its excellent on-chip integrity, low excitation voltage and precise controllability over miniaturized scales. [25][26][27] Efficient and effective fluid mixing, [28][29][30][31] pumping, [32][33][34][35][36] particle manipulation, [37][38][39][40][41] and twophase flow 42,43 have been demonstrated with success, by employing ACEK mechanisms of flow manipulation.…”

Section: Introductionmentioning

confidence: 99%

Directionally controlled open channel microfluidics

et al. 2019

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Free-surface microscale flows have been attracting increasing attention from the research community in recent times, as attributable to their diverse fields of applications ranging from fluid mixing, particle manipulation, to biochemical processing on a chip. Traditionally, electrically-driven processes governing free surface microfluidics are mostly effective in manipulating fluids having characteristically low values of the electrical conductivity (lower than 0.085 S/m). Biological and biochemical processes, on the other hand, typically aim to manipulate fluids having higher electrical conductivities (0.1  S/m). To circumvent the inherent limitation of traditional electrokinetic processes in manipulating highly conductive fluids in free surface flows, here we experimentally develop a novel on-chip methodology for the same by exploiting the interaction between an alternating electric current and an induced thermal field. We show that the consequent local gradients in physical properties as well as interfacial tension can be tuned to direct the flow towards a specific location on the interface. The present experimental design opens up a new realm of on-chip process control without necessitating the creation of a geometric confinement. We envisage that this will also open up research avenues on open-channel microfluidics; an area that has vastly remained unexplored.

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Energy-efficient generation of controlled vortices on low-voltage digital microfluidic platform

Cited by 11 publications

References 20 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

Directionally controlled open channel microfluidics

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