Differential polarization on assembled graphene electrodes for sweat metabolites detection

Real-time sweat analysis is crucial for health and sports monitoring; yet, enzyme-based sensors suffer from instability and frequent recalibration. Here, we present an enzyme-free strategy that exploits differential polarization on structurally distinct graphene electrodes. Direct-written graphene oxide inks were dried to yield a dense graphene film (GF) or porous graphene aerogel (GA), then chemically reduced. Electrochemical characterization revealed two regimes: GA with low charge-transfer resistance and high surface area and GF with higher resistance and lower area, corresponding to mass-transport/adsorption-dominated versus charge-transfer-dominated behavior. Differential pulse voltammetry combined with linear discriminant analysis achieved 100% classification of 12 sweat-relevant analytes and accurately classified human cohorts using a wearable prototype. For quantification, symbolic regression mapped GA/GF features to concentration with near-unity slopes (R² ≈ 0.999) over 0.001-0.10 M for representative analytes. This work demonstrates accurate, enzyme-free identification and quantification of sweat metabolites and outlines a scalable route toward wearable biochemical monitoring.