Reaction surface array diagnostic apparatus

A reaction surface array diagnostic apparatus and method of making the same includes a substrate carrying a plurality of reaction surfaces, a plate and a gasket, each having a plurality of through bores, alignable with one of the reaction surfaces and forming a fluid tight well about each reaction surface when the gasket and the plate are sealingly affixed to the substrate to form a stack. Clamp members engage opposite side edges of a stack to compress the gasket. A plurality of side-by-side disposed clamped stacks of plates, gaskets and substrates are mounted in a tray in the standard footprint of a microtiter plate. Alternately, the plate and the gasket are combined into a single plate formed of a flexible material having an adhesive on one surface.