Wearable Uric Acid Electrochemical Sensor with a Scratched Graphite Electrode

Uric acid levels in sweat are indicative of various health conditions, including gout and cardiovascular diseases. A significant challenge in monitoring uric acid in sweat remains due to the low concentration of uric acid, which necessitates a substantial enhancement in the sensitivity of sensors in an economical manner. Thus, we have developed a new and low-cost method to improve the sensitivity of sensors with a non-smooth graphite surface using a scratched electrode.

Utilizing xurography, we constructed a compact, three-layered graphite sensor suitable for wearable applications, featuring a working electrode, counter electrode, and a reference electrode with a silver/silver chloride coating, all 1mm wide.

To integrate this development with smartphone-based biosensors, the enhanced graphite sensor's electrical signals are transmitted to a smartphone application, enabling the real-time monitoring and data analysis of uric acid levels in sweat. This connectivity not only augments the portability and convenience of health monitoring but also leverages the widespread availability of smartphones to facilitate accessible health management.

In testing, we prepared uric acid solutions in phosphate-buffered saline and measured them using Differential Pulse Voltammetry (DPV) with a PalmSens4 device. Sensors with different surface roughness were tested against uric acid solutions to evaluate their effect on sensitivity.

The results demonstrated that sensors with rougher surfaces detected uric acid at lower limits. Specifically, the limit of detection (LOD) with unscratched working electrodes was 100 µM, while with scratched surfaces, the LOD improved to 25 µM. The DPV profiles showed peak currents of 5.954 µA for smooth-surface sensors and 90.478 µA for roughened-surface ones, when detecting the high-concentration (1000µM) uric acid solution.

In conclusion, increasing the surface roughness of graphite electrodes significantly improves the sensitivity of uric acid detection in sweat. This study presents a low-cost yet effective method to increase the surface roughness, providing a reference for the more efficient fabrication of wearable uric acid sensors.