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

Abstract

With rising hazardous organic vapours in the environment, the detection of volatile organic vapour compounds (VOCs) is becoming important. 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 chemiresistive sensor presented here is fabricated on 2.5~\mu \text{m} thick ultra-flexible graphene oxide-chitosan (GOC) with Pt electrodes having 60~\mu \text{m} gap. The electrostatic interaction and strong hydrogen bonds between GO and polysaccharide groups in chitosan provide tunable hydrophobicity and stability to the droplet. With a conductive droplet of \sim 10~\mu \text{L} of aq. NaCl as an active sensing material dispensed between the Pt electrodes, it was observed that the droplet showed 14-21% change in resistance in the presence of VOCs. A read-out circuit was also designed to get the data from the droplet sensor. The response time for the presented sensor (3-4 seconds) is significantly better than its solid-state sensor counterparts. With attractive features such as disposability, affordability and fast response the presented sensor will find applications in industrial environments, laboratories, health centres, and biomedical devices.