Integrated AC electrokinetic cell separation in a closed-loop device.

We integrate electrothermally induced micro-pumps and dielectrophoretic (DEP) traps into micro-circulating fluidic channel loops for yeast cell concentration and separation, two important on-chip cell manipulation tasks, with the same embedded electrodes on-chip. Each fluidic loop design contains well-defined high and low field regions that serve for both fluid transport and cellular manipulation. From a detailed study into the frequency dependent DEP behavior of viable (live) and non-viable (dead) yeast, we demonstrate several operating modes that utilize positive DEP (pDEP) and negative DEP (nDEP) to concentrate both types of cells at either the high or low electric field region and to separate one cell type to a high-field region and one to a low-field region. Because the cells visit the trapping regions repeatedly with the circulating loop design and because of the high shear rates at these stations, our device offers very rapid cell separation and concentration. Two circulating loop designs--one a four-sided square loop, the other a three-sided triangle, with different spatial symmetries and with linear dimensions less than 1 mm, are presented.