Laser-Induced Graphene Paper-Based Microfluidic Platform for Dual-Mode Electrochemical and Colorimetric Detection of Glucose

Microfluidic paper-based analytical devices (μPADs) provide an attractive platform for diagnostics owing to their low cost, passive fluid transport, and ease of fabrication. However, integrating dual-sensing capabilities into a single paper device while maintaining a simple manufacturing process remains challenging. Here, we present a foldable dual-mode microfluidic paper-based analytical device (DM-μPAD) that integrates laser-induced graphene (LIG)-based electrochemical sensing with enzyme-mediated colorimetric detection. A straightforward laser-patterning strategy was used to fabricate LIG electrodes directly patterned onto the polyimide tape-covered cellulose paper via a one-step laser engraving process, forming a conductive graphene network that serves as an electrochemical sensing module. A screen-printing process was used to form hydrophobic perfluoropolyether barriers, which define capillary-driven microfluidic channels that guide sample transport between sensing regions. The folded architecture enhances fluid-electrode interaction and enables simultaneous electrochemical and colorimetric measurements within a single analytical platform without electrode transfer or complex assembly. This dual-readout technique provides cross-validation of results to enhance detection reliability. The proposed DM-μPAD demonstrated good selectivity against common nonspecific compounds, a wide linear detection range of 0.01 to 3.0 mM, and a low detection limit of 9.23 μM in the electrochemical mode, while displaying a dynamic detection range of 0.1 to 2.0 mM with a detection limit of 57.9 μM in the colorimetric mode. Furthermore, the platform maintained high reproducibility, mechanical flexibility, and environmental stability. This work highlights the potential of laser-induced graphene-based paper microfluidics as a versatile platform for developing portable, cost-effective, and multiplexed biosensing devices.