Enhanced selectivity of microfluidic gas sensors by modifying microchannel geometry and surface chemistry with graphene quantum dots

Among the gas sensing technologies, microfluidic gas sensors have garnered attention because of their sensitivity, compact size, and low cost. In this study, we demonstrate improved selectivity of microfluidic gas sensors toward volatile organic compounds by increasing the effect of adsorption of analytes on the surface of the sensor's microchannel through increasing the ratio of the surface area (in contact with analyte) to the volume of the microchannel. First, the effect of microchannel geometry modification (reduction of width) is studied through a computational parametric approach (which is validated experimentally). The results show an average improvement of 93.44 % and 60.1 % in selectivity toward polar and nonpolar VOCs, respectively. In the next step, the surface of the microchannel is modified with graphene quantum dots, which has a two-fold effect on VOCs adsorption: (i) increasing the surface area, and (ii) adding functional groups. The experimental results of this step show an average improvement of 101.45 % and 98.82 % in the sensor's selectivity for the smallest widths toward polar and nonpolar VOCs, respectively. These results indicate that increasing the ratio of surface area (in contact with analyte) to the volume of the microchannel and adding functionalized nanofeatures to the microchannel surface area are promising ways to enhance the selectivity of microfluidic gas sensors.

Automated summary

This study demonstrates an improved selectivity of microfluidic gas sensors towards volatile organic compounds by increasing the effect of adsorption of analytes on the surface of the sensor's microchannel. Modification of microchannel geometry and surface with graphene quantum dots significantly enhances the sensor's selectivity.