Patent ID: 8623596

Claim:
A microfluidic immunoassay device for detecting and measuring an analyte in a liquid sample, comprising a liquid sample inlet defined by an opening for accepting the liquid sample, said liquid sample inlet in continuous fluid connection with a flow resistor channel, said flow resistor channel in continuous fluid connection with an assay inlet of a reaction chamber, wherein the reaction chamber has adsorbed on its surface a plurality of immobilized antigen-specific antibodies (Ab1) specific to an analyte, wherein the surface of the reaction chamber also has a plurality of magnetic-responsive micro-beads desiccated thereon, each of said plurality of magnetic-responsive micro-beads coated with an antigen-specific antibody (Ab2) specific to the analyte, wherein the plurality of antibody-coated magnetic-responsive micro-beads rehydrate, disperse and bind to any analyte present in the liquid sample when the liquid sample flows through the reaction chamber, wherein any analyte present in the liquid sample also binds to the antigen-specific antibodies immobilized on the surface of the reaction chamber to form Ab1-analyte-Ab2-coated magnetic-responsive micro-bead complexes, and wherein any unbound antibody-coated magnetic-responsive micro-beads exit the reaction chamber through an assay outlet, said assay outlet in continuous fluid connection with a micro-channel splitter which bifurcates to form a calibration micro-channel (Co) and at least one test micro-channel (Cm), said at least one test micro-channel and said calibration micro-channel kept at an equal and constant pressure, said calibration micro-channel in continuous fluid connection with a calibration graduated column, and said at least one test micro-channel in continuous fluid connection with at least one test graduated column, wherein one or more magnets creates a magnetic field gradient, said at least one test micro-channel exposed to the magnetic field gradient which causes flocculation of the magnetic-responsive micro-beads in the at least one test micro-channel which reduces flow rate (Qm) of the liquid sample in the at least one test micro-channel compared to the flow rate (Qo) of the liquid sample in the calibration micro-channel, wherein each of the graduated columns has a graduated scale thereon which provides a read-out of the total sample volume flowing through the test micro-channel, Vm, and the sample volume flowing through the calibration micro-channel, Vo, and collected in each of the graduated columns, which read-out is proportional to the concentration, ρ, of Ab1-analyte-Ab2-coated magnetic-responsive micro-bead complexes, which is a function of the concentration of the analyte in the liquid sample.