Combined Dielectrophoretic/ Electrohydrodynamic/Evanescence bas

A common problem facing the application of dielectrophoresis for practical problems in medicine and biology is that the electric field gradient required to manipulate cells limits both the geometry of the electrodes, the volume of solution over which the device is effective, and the time taken to trap particles on the electrode surface. Furthermore, the nature of the dielectrophoretic force is such that particles generally collect on electrode edges, whereas for many surface detection methods, collection on the metal electrode surface is preferable. In this paper, we present a method of particle collection for enhancement of surface-based biosensors using evanescent light scattering for particle detection, using combined dielectrophoretic forces and electrohydrodynamic fluid flow to concentrate particles onto the central electrode area using relatively large electrode arrays. Bacterial spores of Bacillus subtilis var niger were observed to collect from particle concentrations as low as 5x10 3 spores/ml.