Micro/Bio/Nanofluidics Unit, Okinawa Institute of Science and Technology Graduate University , 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa 904-0495, Japan.
Systems and Process Engineering Centre, College of Engineering, Swansea University , Fabian Way, Swansea SA1 8EN, U.K.
Anal Chem. 2017 Dec 19;89(24):13146-13159. doi: 10.1021/acs.analchem.7b02450. Epub 2017 Nov 10.
Controlling the fate of particles and cells in microfluidic devices is critical in many biomedical applications, such as particle and cell alignment and separation. Recently, viscoelastic polymer solutions have been successfully used to promote transversal migration of particles and cells toward fixed positions in straight microchannels. When inertia is negligible, numerical simulations have shown that strongly shear-thinning polymer solutions (fluids with a shear viscosity that decreases with increasing flow rates) promote transversal migration of particles and cells toward the corners or toward the centerline in a straight microchannel with a square cross section, as a function of particle size, cell deformability, and channel height. However, no experimental evidence of such shifting in the positions for particles or cells suspended in strongly shear-thinning liquids has been presented so far. In this work, we demonstrate that particle positions over the channel cross section can be shifted "from the edge to the center" in a strongly shear-thinning liquid. We investigate the viscoelasticity-induced migration of both rigid particles and living cells (Jurkat cells and NIH 3T3 fibroblasts) in an aqueous 0.8 wt % hyaluronic acid solution. The combined effect of fluid elasticity, shear-thinning, geometric confinement, and cell deformability on the distribution of the particle/cell positions over the channel cross section is presented and discussed. In the same shear-thinning liquid, separation of 10 and 20 μm particles is also achieved in a straight microchannel with an abrupt expansion. Our results envisage further applications in viscoelasticity-based microfluidics, such as deformability-based cell separation and viscoelastic spacing of particles/cells.
控制微流控设备中粒子和细胞的命运在许多生物医学应用中至关重要，例如粒子和细胞的对准和分离。最近，粘弹性聚合物溶液已成功用于促进粒子和细胞在直微通道中向固定位置的横向迁移。当惯性可以忽略时，数值模拟表明，强剪切稀化聚合物溶液（剪切粘度随流速增加而降低的流体）会促进粒子和细胞在具有正方形横截面的直微通道中向拐角或中心线迁移，这取决于粒子大小、细胞可变形性和通道高度。然而，到目前为止，还没有关于悬浮在强剪切稀化液体中的粒子或细胞位置发生这种移动的实验证据。在这项工作中，我们证明了在强剪切稀化液体中，粒子在通道横截面上的位置可以从“边缘到中心”移动。我们研究了刚性粒子和活细胞（Jurkat 细胞和 NIH 3T3 成纤维细胞）在 0.8wt%透明质酸水溶液中的粘弹性诱导迁移。展示并讨论了流体弹性、剪切稀化、几何约束和细胞可变形性对粒子/细胞在通道横截面上位置分布的综合影响。在相同的剪切稀化液体中，在具有突然扩张的直微通道中也实现了 10 和 20μm 粒子的分离。我们的结果设想了基于粘弹性的微流控技术的进一步应用，例如基于变形性的细胞分离和粒子/细胞的粘弹性间隔。
