A continuous cell separator based on gravity force and buoyant force in dissimilar density fluids

Abstract

We present a continuous cell separator to achieve density-dependent cell separation based on the gravity and buoyancy on the cells in dissimilar density fluids. Previous cell separators, based on the size or dielectrophoretic property of the cells, are suitable for size-dependent and density-independent cell separation; however, they can be difficult to collect the same types of cells given the same density but with size variations. In addition, conventional separation by centrifuge have difficulties to integrate into on-chip and to do serial processes after cell separation, which is important for on-chip application. The present separator, however, is capable of collecting the same types of cells based on the cell density using the net force between the buoyancy and gravity of the cells in the fluid. The proposed chip isolates low-density cells at the upper outlet while obtaining high-density cells from the lower outlet. For polystyrene (PS) beads having an identical low density of 1.05 g/ml with different diameters of 6 mu m and 10 mu m the small (6 mu m) and large (10 mu m) beads were collected at the common upper outlet with maximum efficiencies of 97.9 +/- 1.12% and 100%, respectively. For PS beads having an identical size of 6 mu m with different densities of 1.05 g/ml and 1.5 g/ml, the low-density (1.05 g/ml) and high-density (1.5 g/ml) beads were separated at the maximum efficiencies of 87.8 +/- 4.85% and 100% through the upper and lower outlet, respectively. Thus, we verify that the proposed chip achieves cell separation based on density. In addition, WBCs and RBCs were extracted based on density with efficiency levels of 88.86 +/- 1.42% and 86.4 +/- 1.99%, respectively. The present separator has the potential to be used in the pretreatment of whole blood. (C) 2011 Elsevier B.V. All rights reserved.