This study revolves around the lactic acid, whose detection provides information about metabolic state and muscle fatigue. Apart from an initial theoretical section covering electrochemical sensors, the importance of lactate detection, and the role of nanoparticles in sensing, this work presents the development of an electrochemical sensor for lactic acid detection, emphasizing the type of functionalization used with mill-scale nanoparticles to detect acid lactic in real samples. A static sweat sampling approach using droplet method has been employed, reducing setup complexity and need of additional hardware. The results focus on an in vitro characterization using artificial samples, with lactic acid concentrations ranging from 0 mM to 26 mM.