Laser-Induced Graphene Electrochemical Sensors: Plasma Treatment, Lithium-Ion Detection via Printed Surface Modification, and Integrated 3D Printed Microfluidics

Abstract

Laser-induced graphene (LIG) has gained attention as a cost-effective and sustainable alternative to traditional electrochemical sensing electrodes. It enables a simple, one-step fabrication process that eliminates the need for complex materials or procedures. While LIG has attracted significant attention for various sensing applications, its potential for lithium detection remains largely unexplored. Lithium detections are particularly noteworthy given that monitoring is an essential priority in both industrial processes and medical diagnostics. One known limitation of LIG is its hydrophobic surface, which limits sensor performance and was addressed in the first part of this study. Although plasma treatment has been used to improve LIG’s surface wettability, the effect of treatment duration has not been fully explored. Overexposure can introduce surface defects and reduce conductivity. We optimized plasma treatment time to improve surface reactivity while preserving the structural and electrical properties of LIG. In the second part of this study, we developed a lithium-selective sensor to address the increasing demand for reliable lithium detection. To achieve lithium selectivity, we functionalized the LIG electrode with lithium manganese oxide (LMO) using dispense printing for better uniformity of the printed layer. LMO is chosen for its strong interaction with lithium ions. This thesis is the first report of LMO being combined with LIG for lithium sensing. Finally, this study introduced a fully additively manufactured electrochemical sensor that integrated functionalized LIG electrodes with 3D-printed microfluidic channels. By enabling both the formation of conductive LIG patterns and the 3D printing of microfluidic structures directly onto a 3D-printed substrate, this approach removes the need for complex alignment or assembly steps. The successful result is a compact, efficient, and scalable sensing platform that combines the strengths of LIG, lithium-selective functionalization, and additive manufacturing for practical and selective lithium detection.