The freshness of many consumer goods often depends on the humidity inside the packaging. However, incorporating humidity sensors into consumer packaging is currently not feasible because conventional sensors require electronics, a power source and a display.
A humidity sensor being developed at Swiss Federal Institute of Technology (ETH) in Zurich, however, does not require any of these. The device is simply a copper-based strip that changes color when a certain humidity level is reached.
The work is detailed in a Langmuir paper published March 13.
