A Novel Approach to Fabricating Sustainable Enzymatic Lactate Biofuel Cells Using Direct Laser Writing Technology for Wearable Real-Time Monitoring Applications

Lactate is a key biomarker of metabolic activity, with elevated levels serving as indicators of various physiological and pathological states. Continuous monitoring of lactate is therefore essential for both healthcare and performance optimization, while enzymatic biofuel cells (EBFCs) provide a sustainable approach to powering wearable biosensing systems. Despite lactate’s abundance in biofluids, lactate-based EBFCs remain underexplored, particularly on scalable electrode platforms. Here, we report the first lactate/oxygen EBFC fabricated on laser-induced graphene (LIG) electrodes prepared by direct laser writing. The bioanode and biocathode were functionalized exclusively with essential components including lactate oxidase with tetrathiafulvalene and bilirubin oxidase with ABTS, respectively. The device exhibited an open-circuit potential (OCP) of about 600 mV and a maximum power density of 48.1 µW·cm ^-2 at 20 mM lactate. Importantly, the power density increased linearly with lactate concentration across the physiologically relevant sweat range (5–20 mM, slope 2.9 µW·cm ^-2 ·mM□ ¹ , R ² = 0.997), underscoring its suitability for sweat-based biosensing. These findings demonstrate the viability of LIG as a sustainable and scalable electrode material and highlight the potential of simplified EBFC architectures for future integration into wearable and self-powered biosensing technologies.