An On-Chip,
Multichannel Droplet Sorter Using Standing
Surface Acoustic Waves
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Abstract
The
emerging field of droplet microfluidics requires effective
on-chip handling and sorting of droplets. In this work, we demonstrate
a microfluidic device that is capable of sorting picoliter water-in-oil
droplets into multiple outputs using standing surface acoustic waves
(SSAW). This device integrates a single-layer microfluidic channel
with interdigital transducers (IDTs) to achieve on-chip droplet generation
and sorting. Within the SSAW field, water-in-oil droplets experience
an acoustic radiation force and are pushed toward the acoustic pressure
node. As a result, by tuning the frequency of the SSAW excitation,
the position of the pressure nodes can be changed and droplets can
be sorted to different outlets at rates up to 222 droplets s<sup>–1</sup>. With its advantages in simplicity, controllability, versatility,
noninvasiveness, and capability to be integrated with other on-chip
components such as droplet manipulation and optical detection units,
the technique presented here could be valuable for the development
of droplet-based micro total analysis systems (μTAS)