Microfluidic and nanofluidic devices, systems, and applications

A method comprising:

• a) providing a microfluidic device comprising:
• i) at least one microfluidic circuit, wherein the at least one microfluidic circuit comprises:
• (A) a first microfluidic channel;
• (B) a first port;
• (C) a second port;
• (D) a first valve, wherein the first valve has a first position and a second position in which the cross-sectional area of the first valve is increased;
• (E) a second channel that converges with the first channel at a nexus, wherein the nexus comprises a valve that, when open, allows for fluid communication between said first and second channels and, when closed, interrupts fluid flow between the first and second channels but not along the first channel, and wherein the second channel is fluidically connected to a third port;
• (F) a reactor;
• and
• (G) at least one diaphragm pump comprising at least three diaphragm valves configured to pump fluid from the first port and the third port into the first valve, into the reactor and into the second port;
• and
• ii) a magnet configured to produce a magnetic field within the first valve;
• b) pumping reagent from the first port and sample from the third port into the first channel to form a mixture;
• c) pumping the mixture into the reactor and performing a chemical or biochemical reaction on the mixture to create a product;
• d) contacting the product in the device with particles, wherein the particles bind the product;
• e) positioning the first valve in the second position;
• f) moving the particles through the first channel into the first valve;
• and
• g) capturing the particles in the first valve with the magnetic field.