Flow channel structure, and mixing method, extraction method, and reaction method for fluids

A flow channel structure for causing a first fluid and a second fluid to flow so as to mix together, comprising a substrate in which a flow channel for causing the first fluid and the second fluid to flow is formed, wherein:

• the flow channel is formed on a top surface of said substrate, and includes a main channel that causes the first fluid to flow along the top surface of said substrate, a plurality of sub channels that are formed on a back surface of said substrate facing the opposite direction to the top surface of said substrate, and causes the second fluid to flow along the back surface of said substrate, and a plurality of merging portions that penetrate said substrate in the thickness direction of said substrate from the top surface side to the back surface side, and merge the second fluid flowing through the plurality of sub channels with the first fluid flowing through the main channel;
• each of the sub channels of the flow channel has an inlet for introducing the second fluid into the sub channel, and the respective inlets are provided independently of one another;
• the inlet and an opposite end of each of the sub channels are arranged so as to overlap the main channel at respective positions spaced apart along a direction in which the main channel extends when viewed from a direction perpendicular to the top surface of said substrate;
• and
• each of the merging portions is formed at a position where the main channel and the end of each of the sub channels overlap in said substrate, communicates between the main channel and the end of the sub channel, thereby changing the flow direction of the second fluid flowing through the sub channel connected to the merging portion to the thickness direction of said substrate, and merges the second fluid with the first fluid flowing through the main channel.