Efficient and rapid particle enrichment at the submicron scale is essential for research in biomedicine and biochemistry. Here, we demonstrate an acoustofluidic method for submicron particle enrichment within a spinning droplet driven by a unidirectional transducer. The unidirectional transducer generates intense sound energy with relatively low attenuation. Droplets placed offset in the wave propagation path on a polydimethylsiloxane film undergo strong pressure gradients, deforming into an ellipsoid shape and spinning at high speed. Benefitting from the drag force induced by the droplet spin and acoustic streaming and the radial force induced by the droplet compression and expansion, the submicron particles in the liquid droplet quickly enrich toward the central area following a spiral trajectory. Through numerical calculations and experimental processes, we have demonstrated the possible mechanism responsible for particle enrichment. The application of biological sample processing has also been exploited. This study anticipates that the strategy based on the spinning droplet and particle enrichment method will be highly desirable for many applications.

中文翻译：

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由单向声换能器驱动的旋转液滴内亚微米颗粒的快速富集

亚微米级的高效快速颗粒富集对于生物医学和生物化学研究至关重要。在这里，我们展示了一种用于在由单向换能器驱动的旋转液滴内富集亚微米颗粒的声流体方法。单向换能器以相对低的衰减产生强烈的声能。放置在聚二甲基硅氧烷薄膜上的波传播路径中偏移的液滴会经历强大的压力梯度，变形为椭圆形并高速旋转。受益于液滴旋转和声流引起的拖曳力以及液滴压缩和膨胀引起的径向力，液滴中的亚微米颗粒沿着螺旋轨迹迅速向中心区域富集。通过数值计算和实验过程，我们已经证明了负责粒子富集的可能机制。还开发了生物样品处理的应用。这项研究预计，基于旋转液滴和颗粒富集方法的策略将非常适用于许多应用。