A case for containing a plurality of biological samples contains a base, a substrate and a cover. The substrate is attached to the base and comprises a plurality of reaction regions configured to receive one or more biological samples. The cover comprises an inner surface and is configured to be attached to the base such that the base and cover together provide a cavity containing the substrate. The inner surface includes a central area and a recessed area disposed about the central area. The central area is configured to cover the reaction regions, while the recessed area is offset from the central area in a direction normal to the inner surface.