Piston mechanism, fluid control mechanism and application thereof

A fluid control device, comprising:

• a housing, a sample inlet, and
• a fluid control mechanism, comprising:
• a chamber and a chamber wall, as well as a piston and a piston motion control member provided within the chamber,
• wherein the piston motion control member is provided with external threads forming a screw thread pair with internal threads on the chamber wall, and is configured to rotate along the internal threads to move within the chamber for driving the piston to move in the chamber;
• and
• at least one fluid channel,
• wherein a bottom portion of the chamber is configured to be in communication with the fluid channel,
• wherein an opening connecting the fluid channel and the chamber is arranged at the bottom portion of the chamber, and the piston is configured to be movable to the bottom portion of the chamber to cover the opening, thereby blocking communication between the chamber and the fluid channel,
• wherein a bottom portion of the piston is provided with a piston support, which is configured as a bulge,
• wherein a part of the piston in contact with the bottom portion of the chamber is configured not to cover the opening connecting the fluid channel and the chamber when the piston support is in its natural state;
• and
• the bulge is configured to be flattened due to deformation under pressure, so that the bottom portion of the piston is entirely in complete contact with the bottom portion of the chamber to cover the opening connecting the fluid channel with the chamber, thereby blocking the communication between the chamber and the fluid channel.