Patent ID: 7552741

Claim:
A fluid controlling method for classifying particles by a microfluidic device that includes: an inner flow channel in which an inner fluid flows; an outer flow channel in which an outer fluid flows, the outer flow channel being formed coaxially with the inner flow; a common flow channel in which the inner fluid and the outer fluid flow are in contact with each other, the common flow channel being communicated with, and downstream of, the inner flow channel and the outer flow channel: and a rectifier that adds a flow velocity in a circumferential direction to one of the inner fluid and the outer fluid, the rectifier being positioned between one of the inner flow channel and the outer flow channel and the common flow channel, the rectifier being disposed in one of the inner flow channel and the outer flow channel, and the inner fluid and the outer fluid flowing as laminar flows; the method comprising: sending the inner fluid from the inner flow channel to the common flow channel; and sending the outer fluid coaxially with the inner fluid from the outer flow channel to the common flow channel through the rectifier such that in the common flow channel the outer fluid flows outward of, and coaxially with, the inner fluid; wherein one of the inner fluid and the outer fluid includes a corkscrew flow that flows spirally; and the inner fluid and the outer fluid are in contact with each other, and the inner fluid and the outer fluid are in initial contact with each other at or downstream of the downstream end of the rectifier, and the inner fluid and outer fluid flow as laminar flows, wherein all the inner fluid and outer fluid exits the microfluidic device at the common flow channel exit.