Applications of nanoNewton dielectrophoretic forces using atomic layer deposited oxides for microfluidic sample preparation and proteomics

By increasing the strength of the negative dielectrophoresis (DEP) force, we demonstrate a significantly improved electrokinetic actuation and filtering microsystem. A pinhole-free, nanometer-scale, thin film oxide was deposited using atomic layer deposition, as a protective layer to protect the electrodes from corrosion, when applying high AC voltages (>20 V_pp) at the electrodes. The electrodes were capacitively coupled to the electrolyte buffer by the application of a high frequency AC voltage signal, thus avoiding electric field degradation and the consequent reduction in dielectrophoresis force due to the presence of the insulating oxide layer. In this work, we demonstrated the use of this DEP-enhanced device for two microfluidic applications. First, we demonstrate an on-chip platform for the depletion of cells and highly abundant serum proteins in blood, which is a prerequisite to assay low-abundance protein biomarkers. For the second application, we show 100% detachment of anti-IgG and IgG bound beads (which is on the same order of magnitude in strength as typical antibody-antigen interactions) from the surface, upon the application of the enhanced negative DEP force. This capability offers the possibility of performing a bead-based multiplexed assay against multiple antigen targets where in a single microfluidic channel various regions are immobilized with a different antibody, each targeting a different antigen.