Continuously Electrotriggered Core Coalescence of Double-Emulsion Drops for Microreactions

Hou, Likai; Ren, Yukun; Jia, Yankai; Deng, Xiangyuan; Liu, Weiyu; Feng, Xiangsong; Jiang, Hongyuan

doi:10.1021/acsami.7b00670

Cited by 57 publications

(34 citation statements)

References 41 publications

(74 reference statements)

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“…To achieve continuous and switchable particle concentrating, we ingeniously break the symmetry in converging‐diverging laminar streamlines near the constriction microchannel. A pair of asymmetric oil droplets is arranged at the end of GE, but not on GE, for avoiding complicated electrokinetic stress acting on the oil/water interface of a conductivity gradient , as shown in Fig. B.…”

Section: Resultsmentioning

confidence: 99%

Flexible particle flow‐focusing in microchannel driven by droplet‐directed induced‐charge electroosmosis

Ren

Liu

et al. 2017

Electrophoresis

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We report herein a novel microfluidic particle concentrator that utilizes constriction microchannels to enhance the flow-focusing performance of induced-charge electroosmosis (ICEO), where viscous hemi-spherical oil droplets are embedded within the mainchannel to form deformable converging-diverging constriction structures. The constriction region between symmetric oil droplets partially coated on the electrode strips can improve the focusing performance by inducing a granular wake flow area at the diverging channel, which makes almost all of the scattered sample particles trapped within a narrow stream on the floating electrode. Another asymmetric droplet pair arranged near the outlets can further direct the trajectory of focused particle stream to one specified outlet port depending on the symmetry breaking in the shape of opposing phase interfaces. By fully exploiting rectification properties of induced-charge electrokinetic phenomena at immiscible water/oil interfaces of tunable geometry, the expected function of continuous and switchable flow-focusing is demonstrated by preconcentrating both inorganic silica particles and biological yeast cells. Physical mechanisms responsible for particle focusing and locus deflection in the droplet-assisted concentrentor are analyzed in detail, and simulation results are in good accordance with experimental observations. Our work provides new routes to construct flexible electrokinetic framework for preprocessing on-chip biological samples before performing subsequent analysis.

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Section: Resultsmentioning

confidence: 99%

Flexible particle flow‐focusing in microchannel driven by droplet‐directed induced‐charge electroosmosis

Ren

Liu

et al. 2017

Electrophoresis

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“…The tilde symbol ~ is dropped henceforward for convenience of expression. Within the liquid solution and leaky dielectric blocks, charge conservation in sinusoidal state is given by Equations (3) and (4), respectively [ 66 , 67 , 68 ]:

where the subscripts i = f or s represent the bulk fluid and solid domain, respectively. In this way,

and

denote the electrostatic potential phasor within the solution and block, respectively.…”

Section: Methodsmentioning

confidence: 99%

On AC-Field-Induced Nonlinear Electroosmosis next to the Sharp Corner-Field-Singularity of Leaky Dielectric Blocks and Its Application in on-Chip Micro-Mixing

et al. 2018

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Induced-charge electroosmosis has attracted lots of attention from the microfluidic community over the past decade. Most previous researches on this subject focused on induced-charge electroosmosis (ICEO) vortex streaming actuated on ideally polarizable surfaces immersed in electrolyte solutions. Starting from this point, we conduct herein a linear asymptotic analysis on nonlinear electroosmotic flow next to leaky dielectric blocks of arbitrary electrical conductivity and dielectric permittivity in harmonic AC electric fields, and theoretically demonstrate that observable ICEO fluid motion can be generated at high field frequencies in the vicinity of nearly insulating semiconductors, a very low electrical conductivity, of which can evidently increase the double-layer relaxation frequency (inversely proportional to the solid permittivity) to be much higher than the typical reciprocal RC time constant for induced double-layer charging on ideally polarizable surfaces. A computational model is developed to study the feasibility of this high-frequency vortex flow field of ICEO for sample mixing in microfluidics, in which the usage of AC voltage signal at high field frequencies may be beneficial to suppress electrochemical reactions to some extent. The influence of various parameters for developing an efficient mixer is investigated, and an integrated arrangement of semiconductor block array is suggested for achieving a reliable mixing performance at relatively high sample fluxes. Our physical demonstration with high-frequency ICEO next to leaky dielectric blocks using a simple channel structure offers valuable insights into the design of high-throughput micromixers for a variety of lab-on-a-chip applications.

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“…In this manner, cells in droplets can be sorted, and two different droplets can be coalesced to react. [11,12] The aforementioned research has indicated that droplets generated in microchannels are charged. The charges may be induced by the rubbing action between the aqueous and oil phases during the process of droplet generation and flow.…”

Section: Introductionmentioning

confidence: 99%

Engineering of Droplet Charges in Microfluidic Chips

Ruan

et al. 2020

Adv Eng Mater

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Droplet‐based technologies, which utilize the surface charge characterization of droplets, are used in fluorescence‐activated cell sorting and energy harvesting. Herein, the influence of droplet charges on microchips is investigated via surface engineering. An electrical field is applied to deflect the droplets in a microchannel, thereby enabling a qualitative analysis of the droplet charge. In a glass polydimethylsiloxane (PDMS)‐boned microchip, the droplet charge decreases when the microchannel is changed from a single‐sided to a three‐sided rectangular microstructure. When the ionic concentration of the droplet increases from 1 μm to 10 mm, droplet charges decrease by ≈78%. Meanwhile, a Au film is patterned in the microchannel, and 11‐aminoundecanethiol hydrochloride (AUT) and 12‐mercaptododecanoic acid (MDA) are modified to modulate the Au surface characterization. Compared with the glass–PDMS‐bonded microchannel, the Au film can suppress the streaming potential to decrease the droplet charges. After modification with MDA and AUT, the droplet charges increase. Therefore, the microchannel structures, ionic concentration, and substrate surface properties can be utilized to modulate the droplet charges, which can be widely used in droplet‐based energy harvesting and biological and chemical sample sorting.

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Continuously Electrotriggered Core Coalescence of Double-Emulsion Drops for Microreactions

Cited by 57 publications

References 41 publications

Flexible particle flow‐focusing in microchannel driven by droplet‐directed induced‐charge electroosmosis

Flexible particle flow‐focusing in microchannel driven by droplet‐directed induced‐charge electroosmosis

On AC-Field-Induced Nonlinear Electroosmosis next to the Sharp Corner-Field-Singularity of Leaky Dielectric Blocks and Its Application in on-Chip Micro-Mixing

Engineering of Droplet Charges in Microfluidic Chips

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