Figure 12.

Hydrodynamic effects for selective cell sorting. (A) Hydrodynamic-lift effects are induced by a viscous orthogonally flowing sheath fluid. Height of RBCs (z position in the channel) significantly increases, whereas platelets flow along the wall. (B) Expansion-contraction channels for separating rare cancer cells from blood cells. The combination of inertial lift and viscous drag forces acts on particles of various sizes. The contraction channel aligns the center of inertia of the rare cells (green) toward the channel center, while the other cells are still flowing along the channel walls. (C) Dual role of Dean forces for focusing larger particles (7.32 μm) in a single equilibrium position and transposing smaller (1.9 μm) particles from the inner half to the outer half of the microchannel cross section. (D) Dean flow and centrifugal forces induced by the serpentine channel design induce size-based differential equilibrium positions of the particles. Larger cells migrate toward the center, whereas smaller particles flow along the wall. (E) Obstacles translate cells based on their deformability and viscosity. In the channel, the cells experience a hydrodynamic force and an elastic force as they are being deformed by the ridges. The difference in the gradient of the free energy of soft and stiff cells leads to different transverse forces. These forces deflect the cell trajectories in the microchannel perpendicularly to the ridge, depending on cell stiffness. This method enabled the separation of K562 and Jurkat cells. (F) Randomly distributed particles experience an elastic force, proportional to the particle volume. Large particles migrate toward the centerline. Larger particles laterally migrate farther than smaller particles while flowing in the second stage. (G) Deterministic lateral displacement: particles that are smaller than the lane width follow the streamlines in lane 1, pass through lane 3 in the second row, then pass lane 2 in the third row, flow through lane 1, whereas particles with a radius larger than the width will be displaced repeatedly. (A) Adapted with permission from ref (168). Copyright 2012 the American Institute of Physics. (B) Adapted with permission from ref (169). Copyright 2011 Royal Society of Chemistry. (C) Adapted with permission from ref (165). Copyright 2008 Royal Society of Chemistry. (D) Adapted with permission from ref (172). Copyright 2015 Nature Publishing Group. (E) Adapted with permission from ref (173). Copyright 2013 Wang et al. (F) Adapted with permission from ref (174). Copyright 2015 the American Institute of Physics. (G) Adapted with permission from ref (175). Copyright 2004 the American Association for Advancement of Science.