Assay devices and methods of manufacture

A reaction container in combination with an aqueous reagent, comprising:

• a first polymeric sheet and a second polymeric sheet, each polymeric sheet having an inner planar face and an outer planar face, the inner planar faces of the first and second polymeric sheets being in contact with one another,
• one or more reagent chambers formed in selected portions of the first and/or second polymeric sheets,
• an aqueous reagent sealed in at least one of the reagent chambers, wherein the aqueous reagent is sealed in the reagent chamber at or near the time of manufacture and is stable therein under ambient storage conditions for at least 3 months.