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Issue 17, 2014
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Microfluidic on-demand droplet merging using surface acoustic waves

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Individual droplets can be isolated within microfluidic systems by use of an immiscible carrier layer. This type of two phase systems, often termed “digital microfluidics”, find wide ranging applications in chemical synthesis and analysis. To conduct on-chip biochemical analysis, a key step is to be able to merge droplets selectively in order to initiate the required reactions. In this paper, a novel microfluidic chip integrating interdigital transducers is designed to merge multiple droplets on-demand. The approach uses surface acoustic wave induced acoustic radiation forces to immobilize droplets as they pass from a channel into a small expansion chamber, there they can be held until successive droplets arrive. Hence, no requirement is placed on the initial spacing between droplets. When the merged volume reaches a critical size, drag forces exerted by the flowing oil phase act to overcome the retaining acoustic radiation forces, causing the merged volume to exit the chamber. This will occur after a predetermined number of droplets have merged depending on the initial droplet size and selected actuation power.

Graphical abstract: Microfluidic on-demand droplet merging using surface acoustic waves

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Article information

17 Apr 2014
20 Jun 2014
First published
23 Jun 2014

Lab Chip, 2014,14, 3325-3333
Article type
Author version available

Microfluidic on-demand droplet merging using surface acoustic waves

M. Sesen, T. Alan and A. Neild, Lab Chip, 2014, 14, 3325
DOI: 10.1039/C4LC00456F

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