Impedance Based Microparticle Counter on an Interdigitated Electrode (ide) Surface with Single-bead Sensitivity

An interdigitated electrode (IDE) array-based impedance sensor is developed for microparticle detection. The IDE is fabricated by photolithography, Ti/Au deposition, and dielectric deposition. With this microfabricated IDE array, we demonstrated a highly portable impedance sensing system with frequency analyzing circuits, DAQ, and LabVIEW. With samples containing various microparticle concentrations, impedance values are measured. As the number of microparticles increases, magnitudes of impedance decrease due to current blockage. By obtaining a series of differential magnitudes which are adjusted by a background signal, we found that these differential magnitudes exponentially increase due to the increasing number of microparticles. From these results, number of microparticles on the IDE surface can be precisely counted with a single microparticle resolution. This platform can be extended to use for label-free single particle detection enabling various biological and chemical analyses.