PURPOSE: A method and a device for preparing implantable substrates are provided to have a fluid permeable container that is capable of retaining a biocompatible, implantable substrate, and a driver mechanism for subjecting fluid to a constant force to induce a selected, controlled flow rate of the fluid through a substrate disposed in the container. CONSTITUTION: The device comprises: a reservoir having an inlet and an outlet; a container(12) coupled to the reservoir and having an inlet(22) and an outlet(20), the container being fluid permeable, but capable of retaining a porous, biocompatible, implantable substrate; and a driver mechanism(14) coupled to the container(12) and the reservoir. The driver mechanism(14) is effective to subject any fluid within the reservoir to a constant force so as to induce a selected, controlled flow rate of the fluid through the container. The outlet of the reservoir is coupled to the inlet(22) of the container(12) such that the container(12) is disposed downstream of the reservoir.