Printable fused silica based microchamber integrated with graphene chemi-resistive sensors for direct on-chip soil testing

In this study, we demonstrate a graphene-based portable gas sensor with an integrated fused silica micro chamber for direct on-chip sample injection to detect a low concentration (∼10 ppm) of acetone from a soil sample at room temperature and pressure. A chemiresistive gas sensor was first fabricated by a conformal transfer process using a commercial monolayer graphene film. Printable fused silica micro gas chamber (internal volume of 50 microliter), fabricated separately, was permanently attached with the graphene chemiresistor using an ultra-violet light source. A relative resistance change of 1% (∼20 ppm of acetone) was achieved by injection of a headspace sample for acetone calibration. This direct on-chip injection method shows an excellent potential for detecting volatile organic compounds from a soil sample without requiring complex sample extraction steps.