Capacitive coupled contactless conductivity detection combined with paper-based microfluidic for continuous human sweat rate measurement

Monitoring sweat rate provides valuable insights into an individual’s risk of dehydration, thermoregulation efficiency, and electrolyte balance, particularly relevant for workers in hot environments, athletes, and individuals with certain metabolic conditions. Traditional methods for measuring sweat rates, such as gravimetric techniques, are labor-intensive and unsuitable for real-time monitoring. Capacitive coupling contactless conductivity detection (C4D), a liquid conductivity-measurement technique, offers continuous signal output, high precision, rapid detection, and the advantage of preventing contamination of electrodes or samples. This study proposed an innovative approach integrating C4D with paper-based microfluidics for real-time measurement of sweat rate. Sweat secreted by sweat glands is directed through the microfluidic channels to the C4D electrodes, enabling continuous conductivity monitoring to assess sweat rate. The key parameters were systematically studied, including electrode layout, microfluidic channel structure, and excitation signal characteristics. Furthermore, the effects of sweat volume, electrolyte concentration, and sweating rate on detection accuracy were systematically investigated. To validate the method, we performed practical measurements using simulated sweat, demonstrating that the proposed technique is accurate, rapid, and effective for sweat rate monitoring. This work advances the integration of C4D with paper-based microfluidics, paving a new avenue for its practical application in sweat rate assessment and other health-related monitoring fields.