Magnet-based systems and methods for transferring fluid

A fluid processing cassette for use in combination with a fluid pump including a piston movable toward and away from the fluid processing cassette under operation of a motor, the fluid processing cassette comprising:

• a body defining a rigid portion of a pump cavity;
• a flexible diaphragm associated with and overlying the rigid portion of the pump cavity;
• and
• a magnetized or ferromagnetic material positioned within the flexible diaphragm, wherein
• the flexible diaphragm comprises first and second flexible sheets and the magnetized or ferromagnetic material comprises a magnetized or ferromagnetic member positioned between the first and second flexible sheets,
• the first flexible sheet is entirely separated from the second flexible sheet,
• the magnetized or ferromagnetic member is secured to one or both of the first and second flexible sheets, and
• the first flexible sheet has a size and shape that are substantially the same as a size and shape of the second flexible sheet.

A fluid processing system, comprising:

• a cassette including a body defining a rigid portion of a pump cavity in fluid communication with at least two ports, wherein a flexible diaphragm defines a flexible portion of the pump cavity;
• and
• a fluid transfer assembly to which the cassette is configured to be temporarily secured, wherein the fluid processing system includes a fluid pump comprising
• a motor,
• a piston movable toward and away from the flexible diaphragm of the cassette;
• and
• a linkage connecting the motor and the piston, wherein
• the motor functions to move the piston toward and away from the flexible diaphragm,
• at least a portion of the piston is magnetized and the flexible diaphragm comprises a ferromagnetic material positioned within the flexible diaphragm or said at least a portion of the piston is formed of said ferromagnetic material and the flexible diaphragm comprises a magnetized material positioned within the flexible diaphragm so as to magnetically couple the piston and the flexible diaphragm,
• the rigid portion of the pump cavity includes a lower, substantially frusto-conical portion positioned adjacent to the flexible diaphragm and an upper, substantially cylindrical portion spaced from the flexible diaphragm by the lower, substantially frusto-conical portion, the upper, substantially cylindrical portion being aligned with the magnetized or ferromagnetic material positioned within the flexible diaphragm and with the piston when the cassette is secured to the fluid transfer assembly and configured to receive at least a portion of the magnetized or ferromagnetic material positioned within the flexible diaphragm when the piston is moved toward the flexible diaphragm,
• a diameter of the upper, substantially cylindrical portion is substantially equal to a minimum diameter of the lower, substantially frusto-conical portion and approximately equal to a diameter of the magnetized or ferromagnetic material positioned within the flexible diaphragm,
• the upper, substantially cylindrical portion includes a closed upper end, and
• the body of the cassette defines at least two flow channels, with each flow channel extending between a different one of said at least two ports and the lower, substantially frusto-conical portion.