System for indicating exposure to preselected temperatures or tampering

摘要

Disclosed is a device for selectively indicating strain comprising a layer of polymeric binder and, distributed in or adjacent to the binder layer, microcapsules containing an indicating means, whereby when the binder is stiff, minor flexure of the device causes rupture of the microcapsules and releases the indicating means. This device has a non-stiff state such that a given strain applied to the binder layer in the non-stiff state will not release the indicating means, and a stiff state such that the same given strain applied to the binder layer in the stiff state will release the indicating means. Also disclosed is a method for determining exposure of an article to a given low temperature.