Flexible passive wireless sensor for spoilage detection of packaged goods

Abstract

A pH sensor for determining food freshness may include a substrate and a working tag on the substrate. The working tag may have a first resonant frequency. A reference tag may also be on the substrate. The reference tag may have a second resonant frequency. The pH sensor may further include a first layer in contact with a portion of the working tag and not the second tag. The first layer may be water soluble. The pH sensor may include a second layer positioned on top of the first layer, the second layer configured to dissolve when exposed to an environment having a pH level higher than a threshold pH. Dissolution of the second layer may cause a change in the resonant frequency of the working tag.

Dependencies are inferred from the claim text.