Abstract: A diagnostic test device is provided including a plate having at least one well, preferably a plurality of wells, each with an open bottom across which a composite membrane comprising three layers is placed, with a hydrophobic, liquid-tight seal provided at the periphery of each well. The composite membrane from the top of upstream side to the bottom or downstream side, in sequence, includes a first reaction or filtration layer formed from a thin, liquophilic, microporous membrane, a second or sealing layer, preferably a hydrophobic material in sheet or fiber form, such as nonwoven polypropylene fibers, and a liquophobic, preferably hydrophobic, barrier layer having one or more apertures which allows liquid to exit the well while eliminating lateral migration of a pendant liquid drop. The liquophobic seal provided by the liquophobic sealing layer eliminates "cross-talk" by lateral diffusion or wicking.

Abstract: A chemically active membrane having a large surface area is provided in which a hydrophilic, microporous, skinless, polyamide membrane is chemically bound to a residue of an activating agent which is capable of reacting with a biologically active material.The chemically active membrane, formed by reacting a hydrophilic, microporous, skinless, polyamide membrane with an activating agent may be used to prepare a biologically active membrane having a large surface area which comprises an acceptor molecule such as a monoclonal antibody, a polyclonal antibody, an antigenic substance, a glycoprotein, Protein A, a lectin, a carbohydrate, an enzyme substrate, a cofactor, an inhibitor, a hormone, an IgG class of immunoglobulin, a carrier protein, a receptor, heparin, a coagulation factor, or a histone covalently bound to the hydrophilic, microporous, skinless, polyamide membrane by reacting the chemically activate membrane with the acceptor molecule.