A microfluidic detection system for detection of target entities in a fluid containing a quantity of magnetic beads and a quantity of target entities bound to one or more magnetic beads, in which each target entity bound to a magnetic bead has a smallest effective dimension greater than a largest effective dimension of each magnetic bead, the system comprising: a pump ; a magnet , and a detector component including: a body defining a reservoir ; and a plate disposed within said reservoir and separating said reservoir into a first chamber and a second chamber , said plate defining a plurality of openings therethrough, each opening having an effective dimension sized to permit passage of the largest effective dimension of each magnetic bead and further sized to prevent passage of the smallest effective dimension of each target entity; wherein said first chamber of said reservoir has a first inlet and a first outlet , wherein said first inlet is fluidly connectable to a source of the fluid containing the target entities; wherein the magnet is affixed to or supported relative to the outside of the detector component and disposed relative to said reservoir so that said second chamber of said reservoir and said plate are situated between said magnet and said first chamber of said reservoir, wherein said magnet is configured to generate a magnetic force sufficient to attract magnetic beads in said first chamber of said reservoir to said second chamber of said reservoir; and wherein the pump is suitable for flowing the fluid from the source of the fluid containing the target entities through said first chamber of said reservoir. a pump ; a magnet , and a detector component including: a body defining a reservoir ; and a plate disposed within said reservoir and separating said reservoir into a first chamber and a second chamber , said plate defining a plurality of openings therethrough, each opening having an effective dimension sized to permit passage of the largest effective dimension of each magnetic bead and further sized to prevent passage of the smallest effective dimension of each target entity; a body defining a reservoir ; and a plate disposed within said reservoir and separating said reservoir into a first chamber and a second chamber , said plate defining a plurality of openings therethrough, each opening having an effective dimension sized to permit passage of the largest effective dimension of each magnetic bead and further sized to prevent passage of the smallest effective dimension of each target entity; wherein said first chamber of said reservoir has a first inlet and a first outlet , wherein said first inlet is fluidly connectable to a source of the fluid containing the target entities; wherein the magnet is affixed to or supported relative to the outside of the detector component and disposed relative to said reservoir so that said second chamber of said reservoir and said plate are situated between said magnet and said first chamber of said reservoir, wherein said magnet is configured to generate a magnetic force sufficient to attract magnetic beads in said first chamber of said reservoir to said second chamber of said reservoir; and wherein the pump is suitable for flowing the fluid from the source of the fluid containing the target entities through said first chamber of said reservoir. <EOS>