We present a novel cell detection device based on a magnetic bead cell assay and microfluidic Coulter counting technology. The device can detect specific target cells ratios, as well as cells size distribution and concentrations. The device consists of two identical micro Coulter counters separated by a fluid chamber where an external magnetic field is applied. Target cells conjugated with magnetic beads are retarded by the magnetic field; transit time of a target cell passing through the second counter is longer than that through the first counter. In comparison, a non-target cell transit through two counters with nearly the same time. We demonstrated the transit time delay increased approximately linearly with the increasing target cell concentration. The limit of detection (LOD) of the assay was estimated to be 5.6% in terms of target cell ratio.
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