Dual transduction on a single sensor for gas identification

Poor selectivity is one important limitation of gas sensors based on chemisorption or physisorption. This poor selectivity is usually tackled through the use of a gas sensor array, whose individual elements have diverse selectivity. Gas identification can be achieved by analyzing the unique response patterns of the sensor array. However, such an approach is costly due to its complexity. In this paper, we investigate an alternative solution enabling single sensor gas identification through the integration of two transduction mechanisms in one sensor. We demonstrate this approach through the design of a novel dual transduction gas sensor capable of simultaneously detecting gas-induced variations in the mass and resistance of the sensing material. The relative independence of acquired gravimetric and resistive responses is shown to enable subsequent gas identification. In addition, the proposed approach can also improve the overall limit of detection (LOD) to different gases by exploiting the individual responses with the best LODs. The proposed dual transduction gas sensor was implemented by integrating a film bulk acoustic wave resonator (FBAR) together with interdigitated electrodes. A configurable dual-mode oscillator circuit is also proposed to simultaneously read-out both responses from the sensor.