A device isolates a substance from blood. The substance includes particles with an effective diameter that is within a range defined by effective diameters of constituents of blood. The device comprises a first sheet of graphene including a first plurality of apertures. The first plurality of apertures are configured to pass objects with an effective diameter less than or equal to the effective diameter of the particles of the substance. The device comprises a second sheet of graphene including a second plurality of apertures. The second plurality of apertures are configured to pass objects with an effective diameter less than the effective diameter of the particles of the substance. The device may be configured to include a conduit system. The device may be configured to operate according to a reversible cycle.
