Highly Integrated Graphene-Based Chemical Sensing Platform for Structural Monitoring Applications

Abstract

Two-dimensional materials, such as graphene, hold promise for sensing applications. Graphene's remarkable surface-to-volume ratio, when employed as a transducer, enables the sensor channel to be readily modulated in response to chemical changes in proximity to its surface, effectively converting chemical signals into the electrical domain. However, their utilization has been constrained due to variations in device-to-device performance arising from synthesis and fabrication processes. To address this challenge, we employ Graphene Field Effect Transistors (GFETs) in developing a robust and multiplexed chemical sensing platform. This platform comprises a silicon chip with multiple arrays of sensing units distributed on its surface. This chip is coupled with custom-designed high-speed readout electronics for structural monitoring applications. For example, in harsh environmental conditions, structures constructed from reinforced concrete may experience degradation due to corrosion, a chemical process initiated by carbonation from atmospheric CO₂ and significant fluctuations in temperature and humidity. Under normal conditions, concrete maintains a pH level within the alkaline range of 13 to 14. However, when subjected to carbonation, its pH decreases to values between 8 and 9. Our platform excels in real-time pH monitoring. By conducting I-V sweep measurements in the sensor channel, we have established a correlation between [H⁺] concentration and the device transfer characteristics, i.e. gate-source voltage (𝑉_𝐺𝑆) at graphene's Dirac point with an accuracy of roughly 97%. Additionally, we evaluate changes in graphene channel resistance induced by pH variations. This system and correlation allow for the prompt detection of any deviations induced by corrosion within a concrete environment.