Streamlining Microfluidic Lithium Sensor Fabrication: A Single-Workflow Using Additive Manufacturing and Printed...

Integrated microfluidic electrochemical sensors require seamless combination of electrodes, surface chemistry, and fluid handling, yet most current devices rely on complex, multistep fabrication. We introduce a unified additive manufacturing approach using the high-temperature thermoplastic polyetherimide (PEI), enabling direct formation of laser-induced graphene (LIG) electrodes. Afterward, working electrodes (WEs) are functionalized by dispense printing lithium manganese oxide (LMO) under optimized conditions to achieve uniform coating. The microfluidic channel is then additively manufactured on the same platform using identical printing settings, preserving a single-workflow fabrication process. This approach enables direct tuning of the LIG electrode's selectivity for ion-specific sensing, as demonstrated by lithium detection. For comparison, a baseline LIG electrochemical sensor was first fabricated on polyimide (PI) film consisting of a three-electrode configuration with an LMO-functionalized WE but without a microfluidic channel. The integration of a microfluidic channel significantly enhanced sensing performance, yielding a 31.6% increase in the reduction peak observed in cyclic voltammetry (CV) compared to the baseline nonmicrofluidic device. The developed sensor demonstrates a wide dynamic range of 0.01-10 M, making it suitable for lithium extraction and monitoring applications. The limit of detection (LOD) and limit of quantification (LOQ) were determined to be 9.5 mM and 148 mM, respectively. Furthermore, the sensor exhibits high specificity and selectivity toward lithium in the presence of common interfering ions. These results show that additive manufacturing combined with electrode functionalization offers a practical route for manufacturing LIG-based microfluidic electrochemical sensors targeting specific ions, exemplified here by lithium.