Real-time sensing of lead with epitaxial graphene-integrated microfluidic devices

• Published in: Sensors and actuators. B, Chemical Chemical, 2019-06, Vol.288, p.425-431
• Main Authors: Santangelo, M.F., Shtepliuk, I., Filippini, D., Ivanov, I.G., Yakimova, R., Eriksson, J.
• Format: Article
• Language: English
• Subjects: 3D printed lab-on-chip; Density functional theory; Detection; Epitaxial graphene; Epitaxial growth; Extreme sensitivity; Graphene; Heavy metals; Heavy metals detection; Lead; Liquid phases; Low concentrations; Mathematical analysis; Microfluidic devices; Prototyping; Real time monitoring; Reproducibility; Sensitivity analysis; Silicon carbide; Silicon substrates; Three dimensional printing
• ISSN: 0925-4005; 1873-3077; 1873-3077
• DOI: 10.1016/j.snb.2019.03.021

•Robust and compact 3D printed microfluidic lab-on-chip.•Miniaturised sensing system using 3D printed chip and epitaxial graphene sensors.•Continuous real-time monitoring of toxic heavy metals.•LoD much lower than recommended limit provided by WHO for drinking water.•Response was stable and reproducible over time. Since even low concentrations of toxic heavy metals can seriously damage human health, it is important to develop simple, sensitive and accurate methods for their detection. Graphene, which is extremely sensitive to foreign species, is a key element in the development of a sensing platform where low concentrations of analyte have to be detected. This work discusses the proof of concept of a sensing platform for liquid-phase detection of heavy metals (e.g. Pb) based on epitaxial graphene sensors grown on Si-face 4H-SiC substrate (EG/SiC). The sensing platform developed includes a microfluidic chip incorporating all the features needed to connect and execute the Lab-on-chip (LOC) functions using 3D printing fast prototyping technology. Herein, we present the response of EG to concentrations of Pb2+ solutions ranging from 125 nM to 500 μM, showing good stability and reproducibility over time and an enhancement of its conductivity with a Langmuir correlation between signal and Pb2+ concentration. Density functional theory (DFT) calculations are performed and clearly explain the conductivity changes and the sensing mechanism in agreement with the experimental results reported, confirming the strong sensitivity of the sensor to the lowest concentrations of the analyte. Furthermore, from the calibration curve of the system, a limit of detection (LoD) of 95 nM was extrapolated.