Dual‐Ion Potentiometric Sensor with Laser‐Synthesized AuNPs Onto LIG and Inkjet‐Printed Electrodes for Simultaneous Na⁺ and K⁺ Monitoring in Biofluids

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Accurate monitoring of sodium (Na⁺) and potassium (K⁺) ions is vital for diagnosing electrolyte imbalances associated with physiological disorders. We report a dual‐ion potentiometric sensing platform that integrates laser‐induced graphene (LIG), in situ laser‐synthesized gold nanoparticles (AuNPs) on LIG substrate, and inkjet‐printed all‐solid‐state ion‐selective electrodes (ISEs) for simultaneous Na⁺ and K⁺ detection. Fabricated on a miniaturized microfluidic substrate with a dual‐channel design, this device enables simultaneous measurement of both ions from a single sample. A CO 2 laser irradiation first converts polyimide (PI) into LIG, while a second laser pass simultaneously synthesizes AuNPs in situ and re‐engraves the LIG surface. This interface produces a porous and hydrophobic morphology that enhances the electroactive area, charge‐transfer kinetics, and potential stability. Potentiometric signals are acquired within 100 s using a portable bipotentiostat and transmitted wirelessly via Bluetooth to a smartphone. The sensor displayed near‐Nernstian sensitivities of 59.5 mV decade −1 (Na⁺) and 59.8 mV decade −1 (K⁺), wide linear ranges, excellent repeatability, and low detection limits of 10 µм (Na⁺) and 7.9 µм (K⁺). Validation with human urine samples confirmed its analytical reliability. This work demonstrates a simple and cost‐effective strategy for electrolyte monitoring, offering strong potential for point‐of‐care diagnostics and field‐based health monitoring.