Department of Bioengineering, University of Illinois at Chicago, 851 S. Morgan Street, 218 SEO, Chicago, IL 60607, USA.
Lab Chip. 2018 Dec 18;19(1):147-157. doi: 10.1039/c8lc00973b.
A wide range of microfluidic devices for single stream focusing of cells and particles has emerged in recent years, based on both passive and active methods. Inertial microfluidics offers an attractive alternative to these methods, providing efficient and sheathless passive focusing of cells and beads. Nevertheless, in rectangular microchannels, the presence of multiple equilibrium positions necessitates complicated solutions involving manipulation of the 3D structure in order to achieve single stream flows. Here, we present a new approach to single-stream inertial focusing based on a triangular microchannel geometry. Changing the channel cross-sectional shape leads to asymmetry in the velocity profile, resulting in a size-dependent single stable equilibrium position near the channel apex. We demonstrate that soft lithography masters for such microchannels can be fabricated using PMMA through micromilling, and 15 μm diameter beads can be efficiently focused into a single stream. Confocal microscopy was used to confirm the focusing positions in the microchannel cross-section. We further integrated this device with a laser counting system to form a sheathless flow cytometer and demonstrated the counting of beads with an ∼326 s -1 throughput. The use of a triangular cross-section offers a number of benefits, including simplicity of the fundamental principle and geometry, control of design, a small footprint, and ease of integration, as well as high-precision single position focusing.
近年来，基于被动和主动方法，已经出现了各种用于单细胞和颗粒单流聚焦的微流控装置。惯性微流控技术为这些方法提供了一种有吸引力的替代方法，可实现细胞和珠子的高效无鞘被动聚焦。然而，在矩形微通道中，存在多个平衡位置，需要涉及操纵 3D 结构的复杂解决方案，以实现单流流动。在这里，我们提出了一种基于三角形微通道几何形状的单流惯性聚焦新方法。改变通道横截面形状会导致速度分布的不对称，从而导致在通道顶点附近产生与尺寸相关的单稳定平衡位置。我们证明可以通过微铣削使用 PMMA 制造这种微通道的软光刻母版，并且可以有效地将 15 μm 直径的珠子聚焦成单一流。共聚焦显微镜用于确认微通道横截面中的聚焦位置。我们进一步将该装置与激光计数系统集成，形成无鞘流式细胞仪，并演示了以约 326 s -1 的吞吐量对珠子进行计数。三角形横截面的使用具有许多优点，包括基本原理和几何形状的简单性、设计的可控性、占地面积小、易于集成以及高精度的单位置聚焦。
