4-D dielectrophoretic handling of Janus particles in a microfluidic chip

Janus particles are dissymmetric systems with 2 faces that could present 2 different physical/chemical properties, offering new possibilities in microfluidic research fields. This work presents a novel approach of handling the rotation of Janus particles with dielectrophoresis in a determined location at the single level. We first present the manufacturing process of those particles with fluorescent PS beads coated on one side with Au. Then spectroscopic studies investigate their optical responses under fluorescence excitation as a mean to monitor their rotation angle. Finally, Janus particles are injected in an electro-microfluidic chip exerting non-uniform localized electrical fields inside the channel. The microfluidic experiment shows that not only precise 3D localization of those particles can be achieved but moreover that their rotation can be controlled by the gradient of the applied electrical field. (C) 2009 Elsevier B.V. All rights reserved.