Cell Allignement Under Unidirectional Electropulsation In A Microfluidic Device

The movement of cells under an electric field is widely practiced in microfluidics. The specific characteristics of the cell trajectory are strongly affected by the properties of the electric field (EF) and the cell surface. Cell surface is covered by glycoconjugates that may be potentially charged depending on the pH. Cells that are exposed to a unidirectional EF typically move in one direction due to electrophoresis and electroosmotic flow. In the report, we demonstrate a microfluidic device, in which unidirectional, homogeneous dc pulses drive eukaryotic cells to align at the center of a sealed chamber. Cells were scattered in a microfluidic chamber which had two microfabricated gold electrodes positioned at the two ends of the chamber. The chamber was sealed up during the period when multiple dc pulses of the same direction were applied. We observed interesting movement of cells at various parts inside the chamber toward the center. We postulate that electrochemical effects dominate the tiny space and the generated pH gradient determines the cell surface charge at a local spot and produces the surprising concentration effect. This novel manipulation of a low number of cells in a microfluidic environment may have important applications to a number of cellular studies.