Wristwatch Sensor Tracks Sweat Sodium and Potassium Continuously
Researchers at Tokyo University of Science developed a wristwatch-style device that measures sodium and potassium levels in sweat. It uses a printed reference electrode with a liquid junction containing silica gel for quick stabilization, along with a fabric and superabsorbent fiber layer to transport samples. The sensor connects to custom electronics that can transmit data wirelessly and store it locally on a micro-SD card.
The team was led by Isao Shitanda of Tokyo University of Science, with Takuma Fujisawa as co-author. Their paper appeared online in ACS Omega on September 21, 2026. The wristwatch combines printed sodium- and potassium-selective electrodes with a liquid-junction reference electrode containing silica gel, plus a fabric and superabsorbent fiber layer that moves sweat across the sensing area.
In a construction-site trial, one worker wore the device through normal tasks, breaks, meals, and hydration for about two hours and forty-five minutes. Signals were sent wirelessly to a computer and saved on a micro-SD card. The team cautions that converting readings into exact concentration values would need controlled sweating trials and further validation.
This kind of wearable may eventually help workers, athletes, and outdoor laborers monitor hydration without pausing activity. If validated, it could support earlier awareness of electrolyte loss in hot conditions, potentially benefiting occupational safety and sports performance. However, usefulness may depend on accuracy, comfort, cost, and data privacy. It is unlikely to replace medical testing soon, but could inform personal and workplace hydration practices.