A 3-D microelectrode system for handling and caging single cells and particles

We have designed and constructed several designs of 3-D microelectrode systems consisting of two layers of electrode structures separated by a 40 μm thick polymer spacer forming a flow channel. The electrode elements such as funnel, aligner, cage and switch are driven by alternating current (AC) and/or rotating electric fields. They are designed to focus, trap and separate eukaryotic cells (Jurkat) or latex particles with a diameter of 10–30 μm using negative dielectrophoresis (nDEP). The electrode width is ∼10 μm and active electrode surfaces have been minimised in order to reduce heating of the solution. A more flexible employment of the different electrode elements was realised by working with up to three generators, and/or a laboratory-made distribution box. The electrodes of the funnel, aligner or switch were operated with 5–11 V at 5–15 MHz, efficient handling of particles could be achieved with flow rates up to 3500 μm/s. Cells could be aligned effectively at flow rates up to 300 μm/s in PBS. Latex particles could be retained within the dielectric field cages (DFC) or aligner against a laminar flow of 40–200 μm/s using an amplitude of 8 V at 5–15 MHz. Cells could be held at flow rates up to 50 μm/s. Numerical calculations for dielectric forces and the induced membrane potential in field cages are given for solutions of different conductivities at different applied frequencies.