Capillary Condensation Based Wireless Volatile Molecular Sensor

In this paper, a LC (inductor capacitor) wireless gas sensor is demonstrated for the identification of volatile organic compounds (VOC's) in the air environment. A near-field LC resonant tank consisting of an interdigitated capacitor fabricated on a porous flexible substrate coupled with an inductor coil is used as a sensor and its resonance is interrogated using an external pick up coil. The porous substrate enables capillary condensation of volatiles leading to a change in effective dielectric constant of the substrate which in turn shifts the resonance frequency. The designed sensor has multiple reuse capability and is applicable for continuous monitoring of volatiles such as methanol, iso-propyl alcohol, acetone and n-octane. The proposed sensor can wirelessly detect a 0.15 cc volume of volatiles in air making it highly sensitive. These sensors can be integrated with passive RFIDs in an array format for simultaneous detection of multiple volatile gases similar to an electronic nose. It can also be integrated with food packages to detect volatiles from food along the supply chain for quality control applications.