Method and apparatus for pumping a fluid using magnetic pistons

An apparatus and method are disclosed for pumping fluids such as stress sensitive particles. The apparatus comprises an annular tube having an inlet port and an outlet port, a first and a second permanent magnet piston contained within the tube and means for producing movable magnetic fields for controlling the movement of each of the first and second permanent magnet pistons in the tube. During operation a stationary magnetic field holds the first permanent magnet piston at a position between the inlet port and the outlet port forming a seal at that position and a travelling magnetic field causes the second permanent magnet piston to rotate about the tube. The movement of the rotating piston causes fluid to be drawn in through the inlet port and expelled from the outlet port. The moveable magnetic fields are configured so as to cause the rotating piston, on completing a rotation, to take the place of the stationary piston, whereupon the formerly stationary piston is caused to rotate about the tube in a cyclical fashion.