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An adhesion-based cell-separation device is developed for the extraction of rare cells from a cell mixture. The cell-separation principle mimics leukocyte recruitment from blood vessels in our body, where leukocytes are decelerated by antigen-antibody interaction at the sites of inflammation or injury. Separation of cell mixture can be accomplished by simply introducing the sample plug through an antibody-immobilized microchannel without any pre- or postprocessing. A new class of amino-functionalized parylene (diX AM) is employed in order to provide amino group on the channel-wall surface. The amount of immobilized biomolecules on diX AM surface is characterized through quartz-crystal-microbalance measurements. The number density of immobilized biotin is as large as , which indicates an amount of amino group enough to immobilize biotin and other biomolecules in a closely packed state. It is shown by the measurement of cell velocity in the CD31-coated diX AM microchannel that the flowing velocity of human endothelial cells are reduced by up to 70% due to specific adhesion of CD31 antigens and antibodies. The results are further analyzed by using a 2-D membrane-peeling model, with which the cell velocity can be estimated under different conditions of antibody number density and bulk mean velocity. Based on the experimental results, a cell-separation device for treating a 1- cell-mixture plug is designed and microfabricated. A mixture of human endothelial cells and leukocytes is successfully separated into plugs of each cell type within a shorter period of time as compared to conventional cell-separation methods which require sample preprocessing.