A microfluidic chip with an array of pillars for directing flow of beads is used to measure reaction kinetics. A stream may be continuously drawn from the reaction volume into the microfluidic chip. The bead is attached to a primary antibody. The reaction volume has an antigen and a second antibody with a label. The primary antibody binds to the antigen, and the secondary antibody binds to the antigen, creating a sandwich of bead, antigen, and label. The binding reactions occur over time in the reaction volume. The beads may be imaged after traversing a laminar wash buffer, and the signal intensity is measured. Each bead provides a kinetic monitoring of the immunoassay over the reaction time at which the bead is removed from the reaction media. Methods and systems are described in this disclosure.