Patent ID: 8906702

Claim:
A microfluidic device for use in performing an assay for the presence of a target analyte in a sample fluid, the device comprising: a reservoir containing a fluidic carrier medium comprising magnetic beads, wherein the magnetic bead surfaces are configured to detectably interact with the target analyte; and a substrate on which there is disposed: a main channel sized to accept said magnetic beads and permit the laminar flow of said fluidic carrier medium at a flow rate of at least 0.1 μl per minute along at least a portion of the main channel, the main channel having an upstream end, a downstream end, and opposing first and second sidewalls normal to said substrate; a first inlet fluidly connected to the upstream end of the main channel and adapted to introduce a laminar flow of said fluidic carrier medium and magnetic beads into the main channel, wherein the first inlet is configured to introduce said fluidic carrier medium into the first sidewall of the main channel; a second inlet fluidly connected to the upstream end of the main channel adapted to introduce a laminar flow of a sample stream comprising a target analyte into the second sidewall of the main channel; a first magnet disposed adjacent to the second sidewall of the main channel and positioned to urge the magnetic beads passing the first magnet from the laminar flow of said carrier medium and into the laminar flow of said sample stream and towards the second sidewall; a second magnet disposed downstream from the first magnet adjacent to the first sidewall of the main channel and positioned to urge the magnetic beads passing the second magnet towards the first sidewall, so that the magnetic beads exit the laminar flow of said sample stream before reaching the downstream end of said main channel; and a detection region disposed downstream of said second magnet and configured to receive said magnetic beads after said beads exit the laminar flow of said sample fluid, wherein the main channel comprises a ridge projecting upwardly from said substrate at or upstream to the first magnet, the ridge separating the fluidic carrier medium from the sample stream, wherein the ridge begins upstream to the first magnet and terminates proximate to the first magnet.