Unidirectional electrical pulses for cell alignment in a closed microfluidic chamber

The transport and manipulation of cells in microfluidic structures are often critically required in cellular analysis. Cells typically make consistent movement in a DC electric field in a single direction, due to a combination of their electrophoretic mobility and electroosmotic flow. Here, we demonstrate that mammalian cells focus to the middle of a closed microfluidic chamber under the application of unidirectional DC pulses. Under the pulses, electrochemical reactions take place and create a nonlinear pH gradient, which affects the cell surface charge. Our approach provides a new and simple method for concentrating mammalian cells at the microscale.