The manipulation of cells and particles suspended in viscoelastic fluids in microchannels has drawn increasing attention, in part due to the ability for single-stream three-dimensional focusing in simple channel geometries. Improvement in the understanding of non-Newtonian effects on particle dynamics has led to expanding exploration of focusing and sorting particles and cells using viscoelastic microfluidics. Multiple factors, such as the driving forces arising from fluid elasticity and inertia, the effect of fluid rheology, the physical properties of particles and cells, and channel geometry, actively interact and compete together to govern the intricate migration behavior of particles and cells in microchannels. Here, we review the viscoelastic fluid physics and the hydrodynamic forces in such flows and identify three pairs of competing forces/effects that collectively govern viscoelastic migration. We discuss migration dynamics, focusing positions, numerical simulations, and recent progress in viscoelastic microfluidic applications as well as the remaining challenges. Finally, we hope that an improved understanding of viscoelastic flows in microfluidics can lead to increased sophistication of microfluidic platforms in clinical diagnostics and biomedical research.

微通道中悬浮在粘弹性流体中的细胞和颗粒的操纵引起了越来越多的关注，部分原因是在简单通道几何形状中单流三维聚焦的能力。对粒子动力学的非牛顿效应理解的改进导致对使用粘弹性微流体聚焦和分选粒子和细胞的探索不断扩大。多种因素，如流体弹性和惯性产生的驱动力、流体流变学的影响、颗粒和细胞的物理特性以及通道几何形状，积极相互作用和竞争，共同控制微通道中颗粒和细胞的复杂迁移行为. 这里，我们回顾了这种流动中的粘弹性流体物理和流体动力，并确定了三对共同控制粘弹性迁移的竞争力/效应。我们讨论了迁移动力学、聚焦位置、数值模拟和粘弹性微流体应用的最新进展以及剩余的挑战。最后，我们希望对微流体中粘弹性流动的更好理解可以提高微流体平台在临床诊断和生物医学研究中的复杂性。