Patent ID: 8192401

Claim:
A medical fluid pump system, comprising: a movable piston head; a cassette comprising a base defining an opening; and a membrane attached to the base covering the opening, the membrane together with the base defining a fluid pump chamber, a flow pathway that leads from the fluid pump chamber to an inlet of the cassette, and a flow pathway that leads from the fluid pump chamber to an outlet of the cassette, the cassette positioned so that the membrane faces the piston head and can be moved by the piston head to change a volume of the fluid pump chamber; and an adhesive disposed between and in contact with the piston head and the membrane, wherein the adhesive has sufficient affinity for the piston head to allow the piston head to retract and deflect the membrane outward to increase the volume of the fluid pump chamber while maintaining adhesive contact with the membrane, and the adhesive has substantially greater affinity for the membrane than for the piston head such that the piston head can be retracted in a manner to separate the piston head from the adhesive without separating the adhesive from the membrane.