Multi-potential laser-induced graphene fluidic paper-based array for in-flow differential analysis of phenolic compounds

: CO2 laser-based technologies are relevant to the sensor scenario; however, integrating arrays of laser-induced sensing systems with paper's fluidic capabilities warrants further investigation. Herein, a CO2 laser plotter was employed to define an integrated, pump-free paper-based microfluidic device that encloses an array of four independent laser-induced graphene (LIG) sensors. The multichannel-LIG fluidic paper-based analytical device (fLIG-PAD) ensures continuous, spontaneous sample flow within the LIG array, where each electrode operates at a different potential simultaneously. The fLIG-PAD enables the quantitative determination of phenolic content in food matrices and the partitioning of the phenolic profile into reactivity classes based on electrochemical reactivity. Initially, the CO2 laser parameters were carefully optimized to maximize the charge transfer of the LIG sensing films while examining the resulting morpho-electrochemical features. The system's electroanalytical performance was tested on several phenolic compounds (PC) commonly found in foods; notable electrocatalytic properties were observed, allowing the differentiation of PC into four reactivity levels by applying different potentials at the various LIG sensors. The fLIG-PAD performs simultaneous flow amperometry measurements in continuous mode thanks to the functional design, providing quantitative responses for PCs' continuous analysis (R2 ≥ 0.990), with fast and complete signal recovery (≤570 s), offering repeatable (RSD ≤12%, n = 8) and reproducible (RSD ≤6.3%, n = 3) measurements. The fLIG-PAD, tested on 17 food samples containing PCs from different chemical classes, enables food classification based on their PC patterns, providing PC content quantification correlated with HPLC-MS/MS (r = 0.97).