<p>Glucose and urea sensing in biological fluids using new materials and devices is still of interest for rapid clinical diagnostics and point-of-care technologies. In this work, a transparent, flexible paper-based photo-microfluidic fuel cell (photoµFC) was evaluated for glucose and urea mixture sensing using a TiO₂/Praseodymium (TiO₂/Pr) composite as the photoanode, aiming to couple photo-assisted oxidation under visible light irradiation. The composite was synthesized by a sol-gel route and characterized by UV/Vis, FTIR, and Raman spectroscopy, thermogravimetric analysis and SEM. Optical analysis revealed a band gap of ∼3.2&#xa0;eV due to the intrinsic TiO₂ transitions with additional absorption signals extending into the visible and near-infrared region, enabling photoresponse under visible irradiation; while SEM images indicated TiO₂ nanoparticles with an average diameter of ~ 50&#xa0;nm coated with Pr nanoparticles uniformly distributed on the surface. The nanocomposite was integrated into a transparent photoµFC. Pr incorporation produced a marked enhancement in photoelectrochemical performance. Under visible illumination, glucose-only fuels delivered the highest output (<i>J</i>_{<i>max </i>}≈ 1.5 × 10^− 1 mA cm⁻²; <i>W</i>_<i>max</i> ≈ 5 × 10^− 2 mW cm⁻²), whereas urea-only fuels showed much lower responses. Mixed glucose/urea solutions exhibited intermediate behavior, with high glucose/urea concentrations representing the best co-fuel condition (<i>J</i>_{<i>max </i>}≈ 0.18&#xa0;mA cm⁻²). In all cases, illumination increased current and power relative to dark operation, confirming that Pr-induced electronic states facilitate visible-light-driven charge separation and accelerate glucose oxidation. These results demonstrate that TiO₂/Pr-based photoµFCs are viable platforms capable of discriminating relevant glucose levels in complex matrices.</p> Graphical Abstract <p></p>