Abstract: A valve comprises a first rigid layer having a substantially planar first surface, a second rigid layer having a substantially planar second surface facing the first surface and a substantially planar third surface opposite the second surface and a flexible layer positioned between the first and second surfaces. A valve chamber is demarcated by a concave surface in the substantially planar first surface and one surface of the flexible layer and at least one first fluid passageway in the first rigid layer opens into the valve chamber at the concave surface to alternatively apply a vacuum and pressure thereto. A fluid chamber is demarcated by another surface of the flexible layer and a concave-convex surface in the substantially planar second surface which comprises an inner circular convex portion and a concentric annular outer concave portion. At least two second fluid passageways in the second rigid layer open into the valve chamber at the convex surface.