Conventional capacitive vapor sensors (chemicapacitors) measure gas concentration by observing changes in capacitance between fixed conductive electrodes. Chemicapacitive sensors are robust devices, but cannot detect water vapor concentration corresponding to less than 2% relative humidity.
The proposed technology is a highly-sensitive chemicapacitor with a vapor absorbing layer. The layer absorbs volatile organic compounds, which increases stress on the interdigitated fingered capacitor and causes the fingers to bend. As the absorption layer approaches the other finger, an electrical signal is produced. This sensitivity increasing method is compatible with pre-existing chemicapacitive sensors, making its potential applications widespread.