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Microdroplet Based Organic Vapour Sensor on a Disposable GO-Chitosan Flexible Substrate

With rising hazardous organic vapours in the environment, the detection of volatile organic vapour compounds (VOCs) is important for human safety. To this end, this paper presents a conductive droplet-based disposable sensor. Unlike conventional sensors, the droplet system is easily replaceable and is capable of detecting multiple vapours based on surface tension gradient. The response time for the presented sensing arrangement was found to be 3-4 seconds which is better than the solid-state counterparts. The chemiresistive sensor used in this work, is fabricated on 2.5 µm thick ultra-flexible graphene oxide-chitosan (GOC) bioresorbable substrate with Pt electrodes which are 60 µm apart. The presence of GO in the GOC substrate provides optimum hydrophobicity to the droplet for efficient operation. The electrostatic interaction and strong hydrogen bonds between GO and polysaccharide groups in chitosan provides tunable hydrophobicity and stability to the droplet. Moreover, biocompatibility, low-toxicity and bioresorbability of GOC substrate are highly desirable in the disposable sensing applications. With a conductive droplet of ~10 µL of aq. NaCl as an active sensing material, dispensed in-between the Pt electrodes, it was observed that the droplet shows 14-21% change in resistance in presence of VOCs.