A method of making an article bonding a layer of deformable material to a surface of a cartridge body having at least one valve body thereon to seal the at least one valve body, the valve body comprising a valve floor and valve walls comprising upper parts, wherein the valve floor is recessed from the surface and the valve walls extend from the surface to the valve floor, and wherein the valve body comprises walls that are curved or sloped in a direction that is non-normal to the plane defined by the surface; and deforming the layer such that upon release of a force causing the deformation, the layer is in contact with the upper parts of the valve walls and is in spaced from the valve floor so as to bias the valve to an open state.