Flow-through assay reaction chamber of cassette has back and forth liquid mixing in narrow gap over array of capture agent, with net flow advance to waste confinement, produced by reversible pumps, operable with rolling diaphragm action with at least limited elastic recovery that advance sample or buffer liquids through conditioning paths before reaching the reaction chamber. The module may include electronics for processing audio andor video signals. The art of adaptation of commercial dehumidification units is taught in design and construction of apparatus for production of freshwater and drinking water.