Dielectrophoresis and microfluidics: Key methods for the manipulation of biological objects ranging from nanoparticles to cells

Cell-based approaches in medicine, biotechnology, and pharmaceutical research offer unique prospects to cope with future challenges in the field of public health. Possible key applications comprise stem cell research, autologous cell therapies, and tissue engineering. Progress will depend on the successful implementation of versatile and flexible tools for the gentle manipulation and characterization of cells. Several requirements have to be met as far as the design of these tools is concerned: they have to be fully compatible with state-of-the-art characterization methods; the cells have to be kept under physiological conditions and their interaction with the environment must be controlled; individual cells must be addressable and identifiable; and finally, it must be possible to perform protocols in the devices in an automated and highly parallel manner. In recent years, microfluidic lab-on-chip systems were introduced that comprise dielectrophoretic microelements for the contactless handling and the analysis of cells and nanoobjects. In this contribution, applications are presented that concern the electrohydrodynamic pumping of media in microchannels and the efficient filtering of nanoobjects such as viruses. We employ linear arrays of microelectrodes for the generation of traveling electric waves in a radio-frequency regime. The activation of cells in microchannels through defined contacts with antibody-coated microbeads and a novel approach for the controlled fusion of cells are also demonstrated.