Five-cross microfluidic network design free of coupling between electrophoretic motion and electro-osmotic flow

Electro-osmotic and electrophoretic interactions are a major concern in the electrokinetic-based microfluidics, in particular, when the electrophoretic mobility of charged particles is greater than the surface electro-osmotic mobility. In this letter, a microfluidic device without surface charge patterning on the channel walls is introduced. Unlike the previous microfluidic devices, the charged particle movements in this five-cross design are largely independent of their charge density and polarity. Different flow patterns (i.e., extensional, mixed shear, and rotational flows) can be generated in this single design and can be quickly switched by just changing the external voltage inputs. The observed flow patterns of charged polystyrene microspheres and lambda-DNA molecules in buffer solutions agree well with simulation results. (c) 2006 American Institute of Physics.