Microfluidic particle focusing has been a vital prerequisite step in sample preparation for downstream particle separation, counting, detection, or analysis, and has attracted broad applications in biomedical and chemical areas. Besides all the active and passive focusing methods in Newtonian fluids, particle focusing in viscoelastic fluids has been attracting increasing interest because of its advantages induced by intrinsic fluid property. However, to achieve a well-defined focusing position, there is a need to extend channel lengths when focusing micrometer-sized or sub-microsized particles, which would result in the size increase of the microfluidic devices. This work investigated the sheathless viscoelastic focusing of particles and cells in a zigzag microfluidic channel. Benefit from the zigzag structure of the channel, the channel length and the footprint of the device can be reduced without sacrificing the focusing performance. In this work, the viscoelastic focusing, including the focusing of 10 μm polystyrene particles, 5 μm polystyrene particles, 5 μm magnetic particles, white blood cells (WBCs), red blood cells (RBCs), and cancer cells, were all demonstrated. Moreover, magnetophoretic separation of magnetic and nonmagnetic particles after viscoelastic pre-focusing was shown. This focusing technique has the potential to be used in a range of biomedical applications.

中文翻译：

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锯齿形微通道中颗粒和细胞的粘弹性聚焦研究

微流控粒子聚焦已成为下游粒子分离、计数、检测或分析样品制备的重要先决条件，并在生物医学和化学领域吸引了广泛的应用。除了牛顿流体中的所有主动和被动聚焦方法外，粘弹性流体中的粒子聚焦由于其固有的流体性质所引起的优势而引起了越来越多的关注。然而，为了实现明确的聚焦位置，在聚焦微米级或亚微米级颗粒时需要延长通道长度，这将导致微流体装置的尺寸增加。这项工作研究了锯齿形微流体通道中粒子和细胞的无鞘粘弹性聚焦。受益于通道的曲折结构，可以在不牺牲聚焦性能的情况下减少通道长度和器件的占地面积。在这项工作中，粘弹性聚焦，包括 10 μm 聚苯乙烯颗粒、5 μm 聚苯乙烯颗粒、5 μm 磁性颗粒、白细胞 (WBC)、红细胞 (RBC) 和癌细胞的聚焦，都得到了展示。此外，显示了粘弹性预聚焦后磁性和非磁性颗粒的磁泳分离。这种聚焦技术有可能用于一系列生物医学应用。和癌细胞，都被证明了。此外，显示了粘弹性预聚焦后磁性和非磁性颗粒的磁泳分离。这种聚焦技术有可能用于一系列生物医学应用。和癌细胞，都被证明了。此外，显示了粘弹性预聚焦后磁性和非磁性颗粒的磁泳分离。这种聚焦技术有可能用于一系列生物医学应用。