Development of a strain-controlled graphene-based highly sensitive gas sensor

Small-size wearable multi-gas sensor with high selectivity and sensitivity is demanded for detecting various harmful gases with high sensitivity in chemical plants, various mines, volcanos, oil and gas fields. Graphene is considered to be the most promising gas-sensitive material due to its large specific surface area and high electron mobility. Many studies have shown that it has a high sensitivity to many gases such as NH3, CO, NO2, H2O, and so on. However, the lack of gas selectivity limits the further application of graphene to gas sensing field. In this study, a first-principle calculation was used to investigate the effect of strain on the gas adsorption behavior of graphene. As a result, it was found that the adsorption behavior of H2O and CO molecules was changed by strain. The adsorption energy of both gases increased monotonically with strain. For carbon monoxide molecules, desorption occurred when the applied tensile strain reached about 5%. These analytical results clearly indicated that there is a possibility of the high selectivity of plural gases by applying appropriate critical strain at which its adsorption changes to desorption. To verify this result, the strain-controlled sensor using graphene was developed. The sensor is composed of graphene and electrodes mounted on a deformable substrate. The high-quality graphene is synthesized on copper by LPCVD (low pressure chemical vapor deposition), and then transferred to the PDMS (Polydimethylsiloxane) substrate using PMMA (Poly methyl methacrylate) as a support layer. It was found that the graphene was monolayer and successfully transferred to the target substrate. The effect of strain on the adsorption of some gases was validated by measuring the change of the resistivity of graphene under the application of uniaxial strain.