New sweat-electrolyte wristwatch logged 2 hours 45 minutes on site

The latest wearable tech story isn’t about steps or calories. Researchers at Tokyo University of Science have developed a wristwatch prototype that gauges the electrolytes in sweat, specifically sodium and potassium, in real time. The aim is to give workers and outdoor enthusiasts a quick, on-wrist signal about hydration status, especially during hot or strenuous work.

Reading sweat accurately has long been tricky. The team solved part of the problem by using a printed reference electrode to speed up stabilization and by adding a silica gel layer to help electrolyte movement. The result is a sensor that doesn’t stall while waiting for readings, with data that can be stored on a memory card or sent to a computer for analysis.

In a real-world test, the researchers wore the device on an active construction site. One worker wore the watch through a typical workday, and the device captured signals from sodium and potassium for about 2 hours and 45 minutes as the person moved around. That shows the approach can work outside the lab, though more validation is still needed.

Is this ready for general use? Not yet. The researchers caution that precise electrolyte readings require more validation and controlled tests before any consumer release. Still, they see it as a starting point for monitoring hydration in jobs like construction, manufacturing, sports, and other outdoor activities without interrupting work. They also suggest pairing electrolyte data with information about sweat rate and water intake to guide hydration, though that combination hasn’t been tested yet.