Channel device and method for concentrating fine particles

A method of increasing a concentration of target fine particles, the method comprising:

• an introducing step comprising introducing a liquid containing fine particles into a main channel;
• a capturing step comprising (i) allowing the liquid to drain into side channels, the side channels each having opposite first and second ends, the first ends of the side channels being connected to opposite side faces of the main channel, and (ii) capturing target fine particles at places where the side channels and the main channel are connected together;
• a releasing step comprising releasing, into the main channel, the target fine particles thus captured;
• and
• a concentrating step comprising allowing the target fine particles thus released to move into a chamber provided at an end of the main channel so that the target fine particles which have increased in concentration are stored in the chamber, wherein
• at least one of a height and a width of each of the side channels is smaller than a particle size of the target fine particles,
• a liquid flow preventer part is provided between the main channel and the chamber, and
• the side channels undergo the following (i) or (ii):
• (i) in the capturing step, application of fluid pressure is carried out so that a pressure at the first ends of the side channels is higher than a pressure at the second ends of the side channels, and, in the releasing step, the application of fluid pressure is stopped or another application of fluid pressure is carried out so that the pressure at the first ends of the side channels is lower than the pressure at the second ends of the side channels;
• or
• (ii) in the releasing step, application of fluid pressure is carried out so that the pressure at the first ends of the side channels is lower than the pressure at the second ends of the side channels.