Splitting a droplet with oil encapsulation using surface acoustic wave excited by electric signal with low power

Zhang, An-Liang; Zha, Yan; Fu, Xingting

doi:10.1063/1.4816464

Cited by 4 publications

(2 citation statements)

References 17 publications

(9 reference statements)

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“…Beyond these simple drop manipulations, in addition to mixing [29][30][31] and drop merging, 32,33 the ability to perform more complex drop operations such as splitting using SAWs in a precise, controllable and reproducible manner have yet to be reported. The splitting achieved in previous attempts by inertially jetting and hence ejecting part of a sessile parent drop to form a displaced daughter droplet, both using SAWs 34 and Lamb waves on superstrates, 35 for example, is difficult to control and is far from precise and reproducible. Where SAWs were combined with electrowetting for drop manipulation, 36 the acoustic field was primarily employed to merely translate the sessile drop to electrodes patterned on the chip where the electric field is able to modify the contact angle and hence split the drop.…”

Section: Introductionmentioning

confidence: 99%

Planar microfluidic drop splitting and merging

2015

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Open droplet microfluidic platforms offer attractive alternatives to closed microchannel devices, including lower fabrication cost and complexity, significantly smaller sample and reagent volumes, reduced surface contact and adsorption, as well as drop scalability, reconfigurability, and individual addressability. For these platforms to be effective, however, they require efficient schemes for planar drop transport and manipulation. While there are many methods that have been reported for drop transport, it is far more difficult to carry out other drop operations such as dispensing, merging and splitting. In this work, we introduce a novel alternative to merge and, more crucially, split drops using laterally-offset modulated surface acoustic waves (SAWs). The energy delivery into the drop is divided into two components: a small modulation amplitude excitation to initiate weak rotational flow within the drop followed by a short burst in energy to induce it to stretch. Upon removal of the SAW energy, capillary forces at the center of the elongated drop cause the liquid in this capillary bridge region to drain towards both ends of the drop, resulting in its collapse and therefore the splitting of the drop. This however occurs only below a critical Ohnesorge number, which is a balance between the viscous forces that retard the drainage and the sufficiently large capillary forces that cause the liquid bridge to pinch. We show the possibility of reliably splitting drops into two equal sized droplets with an average deviation in their volumes of only around 4% and no greater than 10%, which is comparable to the 7% and below splitting deviation obtained with electrowetting drop splitting techniques. In addition, we also show that it is possible to split the drop asymmetrically to controllably and reliably produce droplets of different volumes. Such potential as well as the flexibility in tuning the device to operate on drops of different sizes without requiring electrode reconfiguration, i.e., the use of different devices, as is required in electrowetting-therefore makes the present method an attractive alternative to electrowetting schemes.

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Section: Introductionmentioning

confidence: 99%

Planar microfluidic drop splitting and merging

2015

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“…Technologies such as surface acoustic wave and electrowetting on dielectric have been used to manipulate such droplets, demonstrating a high degree of spatial control. 10 Given their high surface-area to volume ratio, additional steps to limit evaporation must be taken. This can either be achieved by working in a humidied environment 11 or capping the droplets, typically with an immiscible uid such as oil.…”

Section: Introductionmentioning

confidence: 99%

Addressable droplet microarrays for single cell protein analysis

Salehi-Reyhani

Burgin

Ces

et al. 2014

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Addressable droplet microarrays are potentially attractive as a way to achieve miniaturised, reduced volume, high sensitivity analyses without the need to fabricate microfluidic devices or small volume chambers. We report a practical method for producing oil-encapsulated addressable droplet microarrays which can be used for such analyses. To demonstrate their utility, we undertake a series of single cell analyses, to determine the variation in copy number of p53 proteins in cells of a human cancer cell line.

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On the influence of viscosity and caustics on acoustic streaming in sessile droplets: an experimental and a numerical study with a cost-effective method

et al. 2017

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Received XX revised XX accepted XX -To be entered by editorial office)When an acoustic wave travels in a lossy medium such as a liquid, it progressively transfers its pseudo-momentum to the fluid, which results in a steady acoustic streaming. Remarkably, the phenomenon involves a balance between sound attenuation and shear, such that viscosity vanishes in the final expression of the velocity field. For this reason, the effect of viscosity has long been ignored in acoustic streaming experiments. Here, we show experimentally that the viscosity plays a major role in cavities such as the streaming induced by surface acoustic waves in sessile droplets. We develop a numerical model based on the spatial filtering of the streaming source term to compute the induced flow motion with dramatically reduced computational requirements. We evidence that acoustic fields in droplets are a superposition of a chaotic field and a few powerful caustics. It appears that the caustics drive the flow, which allows a qualitative prediction of the flow structure. Finally, we reduce the problem to two dimensionless numbers related to the surface and bulk waves attenuation and simulate hemispherical sessile droplets resting on a lithium niobate substrate for a range of parameters. Even in such a baseline configuration, we observe at least four distinct flow regimes. For each of them, we establish a correlation of the average streaming speed in the droplet, which is increasingly dependent on the bulk wave attenuation as the viscosity increases. These correlations extend our results to a wide range of fluids and actuation frequencies.Key words: Authors should not enter keywords on the manuscript, as these must be chosen by the author during the online submission process and will then be added during the typesetting process (see http://journals.cambridge.org/data/relatedlink/jfmkeywords.pdf for the full list) † Email address for correspondence: michael.baudoin@univ-lille1.fr / Web site:

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Splitting a droplet with oil encapsulation using surface acoustic wave excited by electric signal with low power

Cited by 4 publications

References 17 publications

Planar microfluidic drop splitting and merging

Planar microfluidic drop splitting and merging

Addressable droplet microarrays for single cell protein analysis

On the influence of viscosity and caustics on acoustic streaming in sessile droplets: an experimental and a numerical study with a cost-effective method

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