Lanthanum-doped reduced graphene oxide modified screenprinted carbon electrode for lactic acid sensing

Abstract

This study develops a high-performance lactic acid sensor by modifying screen-printed carbon electrodes (SPCEs) with lanthanum-doped reduced graphene oxide (La-rGO). To enable portable and wearable applications, the sensor is integrated into an internet of things (IoT) architecture utilizing a micro-power analog front-end (AFE), an ESP32-C6 controller, and a fieldprogrammable gate array (FPGA) coprocessor for dynamic calibration. Electrochemical characterization demonstrated a high sensitivity of 20.36 µA·mM⁻¹·cm⁻², surpassing unmodified SPCEs. Under optimal conditions, the sensor achieved a limit of detection (LOD) of 13.58 mM and a limit of quantification (LOQ) of 45.28 mM. Furthermore, hardware evaluation showed the FPGA executes temperature compensation with an ultra-low latency of 1.80 µs. A hybrid duty-cycling strategy restricts the average current to 1.85 mA, allowing over 172 hours of continuous operation on a 320 mAh battery. These results demonstrate the hardware-accelerated, IoT-enabled LarGO/SPCE platform's potential for continuous, non-invasive epidermal sweat analysis.