A peristaltic pump assembly for moving a working fluid. The pump assembly includes an expandable fluid that changes in volume due to the presence of a magnetic and/or electric field. The pump assembly also includes a flexible member interposed between the working fluid and the expandable fluid. The pump assembly further includes a field generator operable to cause the expandable fluid to change in volume by applying the magnetic and/or electric field to the expandable fluid. This, in turn, moves the flexible member to increase the pressure of the working fluid to thereby move the working fluid.