Stretchable Laser-Induced Graphene Electrodes for High-Performance Electrochemical Biosensing of Lactate in Sweat

Laser-induced graphene (LIG) is a versatile, conductive, and highly porous material suitable for use in flexible electronics. However, its application in stretchable devices remains limited due to mechanical and interfacial challenges under strain. Here, we report the development of a stretchable electrochemical sensor based on LIG that maintains electrochemical performance under uniaxial strain up to 20%. The electrode fabrication involves a simple transfer process to elastomeric substrates, which preserves structural integrity and conductivity during deformation. Structural and chemical characterization, including Raman spectroscopy, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and scanning electron microscopy, confirm the characteristic morphology and composition of the LIG network. The electrodes exhibited stable cyclic voltametric responses and maintained their electrochemical characteristics during repeated folding and stretching-relaxation cycles. Moreover, no statistically significant difference in anodic peak current was observed between the relaxed and stretched states (p > 0.05). As a proof of concept, the electrodes were modified with Prussian blue and lactate oxidase for lactate sensing in artificial sweat. The sensor exhibited a linear response range toward lactate (5 to 30 mmol L^-1), effectively covering the clinical window for sweat lactate monitoring and reproducible signals across different deformation states, with a sensitivity of 0.25 μA mM^-1. This work demonstrates the feasibility of fully stretchable LIG-based electrochemical sensors and supports their potential integration into wearable sensing platforms.