The target of this project is the generation of concentration gradients of different agents and the extraction of combinations of agents in a well-defined ratio from the diffusion matrix. The agents should be functional biomolecules, e.g. antibodies, antibody-like molecules or protein ligands that are suspended in water. The concentration gradients are generated by diffusion in microfluidic channels. The diffusion can be influenced by suitable channel geometries and thus adapted to the individual requirements of the task in view.
During removal of the agents, the position information has to be preserved. For this purpose they are attached to micro- or nanoparticles, thus enabling manipulation by dielectrophoresis (DEP) or electroosmosis (EO). Starting from the well-known application of DEP for achieving attraction or repulsion of particles in a field gradient, the concept is extended by replacing the attractive DEP with a pulsed DEP. The pulsed DEP is combined with an EO-flow induced by a second set of electrodes. The advantages of the combined method are that, by pulsed DEP, adhesion of particles on the electrodes is avoided, and by combination with the long-range EO, particles from relatively large volumes can be manipulated by bringing them within reach of the short-range DEP.
  
Left: Microfluidic channels of different widths connecting two reservoirs
Right: Immobilisation of nanoparticles by lithographically defined nanoelectrodes |
