Droplet microfluidics has shown great potential for on-chip biological and chemical assays. However, fluid exchange in droplet microfluidics with high particle recovery is still a major bottleneck. Here, using acoustophoresis, we present for the first time a label-free method to achieve continuous background dilution in droplets containing cells with high sample recovery. The system comprises droplet generation, acoustic focusing, droplet splitting, picoinjection, and serpentine mixing on the same chip. The capacities of the picoinjection and the droplet split to dilute the background fluorescent signal in the droplets have been characterized. The sample recovery at different droplet split ratios has also been characterized. The results show a maximum of 4.3-fold background dilution with 87.7% particle recovery. We also demonstrated that the system can be used to dilute background fluorescent signal in droplets containing either polystyrene particles or endothelial cells.

中文翻译：

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使用声泳在液滴中进行片上背景稀释并实现高颗粒回收率。

液滴微流控技术已显示出用于芯片上生物和化学分析的巨大潜力。然而，具有高颗粒回收率的液滴微流体中的流体交换仍然是主要的瓶颈。在这里，我们使用声泳技术首次提出了一种无标记的方法，可以在含有高样品回收率的细胞液滴中实现连续的背景稀释。该系统包括在同一芯片上的液滴产生，声聚焦，液滴分裂，皮下注射和蛇形混合。皮下注射的能力和液滴分裂以稀释液滴中的背景荧光信号的能力已得到表征。还已经表征了不同液滴分裂比例下的样品回收率。结果显示最大4.3倍本底稀释，颗粒回收率为87.7％。