Environmental Sensing Technology Based on PA

Devices that use for the detection of moisture, radiation, and mechanical abuse can also be fabricated using the same rf antitheft tag technology. In the case of moisture detection, the antenna is again covered with a doped, highly conductive layer of PA, and the device is always in an OFF state. When the tag is exposed to moisture, the conductivity is reduced, which eventually turns the device ON. In the cases of radiation and mechanical abuse detection, a similar design can be employed. Again, the external stimuli (radiation or mechanical forces) serve to release the dopant, and the increased in conductivity leads to a lack of rf response by the tag. 

The thermally induced solid-state polymerization of diacety-lene exhibits a marked change in color as the monomer is polymerized. This behavior has been taken advantage of in the fabrication of a time-temperature indicator [181]. 

---