Multidimensional sorting of microparticles in electrically switchable dielectrophoretic filters

Abstract

The sorting of nano- and microparticles according to different properties is an industrially highly relevant but partly unsolved problem. This thesis investigates whether dielectrophoretic filtration facilitates the sorting of microparticles based on multiple properties. Dielectrophoresis (DEP) is the movement of polarizable particles in an inhomogeneous electric field. The DEP force can be used to immobilize (trap) particles at field maxima located at the surface of a filter medium. To sort particles based on multiple properties, a selective trapping step and several subsequent selective remobilization steps are combined into a batchwise sorting process. Such a complex sorting process is made possible by the increased selectivity of the filter design. Regular filter structures (meshes) are used with pores several orders of magnitude larger than the target particles, so that the particles are trapped solely by the action of positive dielectrophoresis. Compared to other high-throughput DEP filters with irregular porous filter media, a higher selectivity to positive dielectrophoresis was demonstrated. Polystyrene particles could be sorted according to their size, shape, and surface coating in one pass of a DEP filter. The proposed method is therefore a promising technique to efficiently create highly specific particle systems in the future.