Lower threshold temperature indicator device

Abstract

A device for indicating that an ambient temperature has fallen to or below a predetermined lower threshold temperature. The device includes: a porous membrane having first and second spatially separate zones; a first freezable liquid infused in the porous membrane, the first freezable liquid having a freezing point corresponding to the predetermined lower threshold temperature; a second liquid for contacting the first zone of the porous membrane, the second liquid being immiscible with the first liquid; and an indicator window for indicating migration of the second liquid from the first zone to the second zone. The membrane infused with the first liquid is impervious to the second liquid above the threshold temperature and is permeable to the second liquid at or below the threshold temperature. The device is useful in applications where products degrade below a certain lower threshold temperature.

Dependencies are inferred from the claim text.