Patent ID: 7863054

Claim:
A method for detecting or measuring a target substance in a sample solution by using a microfluidic system including: a plate-shaped microfluidic chip having a flow path; a liquid introduction tube for supplying liquid to the flow path, the liquid introduction tube having an end communicating with an end of the flow path and its other end that can be soaked in the liquid that is to be supplied to the flow path; and a liquid discharge head communicating with the other end of the flow path for discharging liquid that has passed through the flow path, wherein the flow path has a dam section having a narrower flow path diameter than other parts of the flow path, the method comprising: soaking an end of the liquid introduction tube opposite the end connected to the flow path in a solution containing beads each having a size preventing the beads passing through the dam section, with a substance having affinity for the target substance being immobilized to the surface of the beads, activating the liquid discharge head, introducing the solution containing the beads into the flow path in the microfluidic chip, and damming the beads at the dam section; soaking an end of the liquid introduction tube opposite the end connected to the flow path in the sample solution; activating the liquid discharge head and introducing the sample solution into the flow path in the microfluidic chip to bring the sample solution in sufficient contact with the beads dammed at the dam section; and detecting or measuring binding between the target substance and the substance having affinity for the target substance that has been immobilized to the bead surface.