Washing and enrichment of particles and cells are crucial sample preparation procedures in biomedical and biochemical assays. On-chip in-droplet microparticle washing and enrichment have been pursued but remained problematic due to technical difficulties, especially simultaneous and precise control over the droplet interface and in-droplet samples. Here, we have achieved a breakthrough in label-free, continuous, on-demand, in-droplet microparticle washing and enrichment using surface acoustic waves. When exposed to the acoustic field, the droplet and suspended particles experience acoustic radiation force arising from inhomogeneous wave scattering at the liquid/liquid and liquid/solid interfaces. Based on these acoustophoretic phenomena, we have demonstrated in-droplet microparticle washing and enrichment in an acoustofluidic device. We expect that the proposed acoustic method will offer new perspectives to sample washing and enrichment by performing the operation in microscale droplets.

中文翻译：

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使用表面声波驱动的声辐射力对液滴进行微粒清洗和富集†

颗粒和细胞的洗涤和富集是生物医学和生化分析中至关重要的样品制备程序。已经进行了片上液滴内微粒的洗涤和富集，但是由于技术上的困难，尤其是同时对液滴界面和液滴内样品进行精确控制，仍然存在问题。在这里，我们在使用表面声波的无标签，连续，按需，液滴内微粒清洗和富集方面取得了突破。当暴露于声场时，液滴和悬浮颗粒会受到声辐射力的作用，该声辐射力是由在液体/液体和液体/固体界面处的不均匀波散射引起的。基于这些声电泳现象，我们已经证明了在声流体装置中液滴的微粒洗涤和富集。