Touchscreen tech tracks body water levels

The holy month of Ramadan is a sacred time when millions of Muslims around the world embark on a profound spiritual journey of fasting, prayer, and reflection. But it is also a time when many face serious health risks, as going without food or water from sunrise to sunset—often in scorching heat—can lead to dangerous levels of dehydration.

Now, scientists at KAUST have found a surprisingly simple way to track the body’s water levels during fasting: by measuring how skin interacts with a touchscreen.

The study is published in the IEEE Sensors Journal.

It is not only useful when fasting. The research team, led by electrical engineer Tareq Al-Naffouri and colleagues at KAUST, showed that the same method applies to athletes, who often experience dehydration due to intense exertion and fluid loss through sweat.

“It is also reasonable to expect that the approach could one day benefit other vulnerable groups, including the very old, the very young, and those with kidney disease,” says Al-Naffouri.

To demonstrate the concept, Al-Naffouri’s team used a basic capacitive sensor—the same type found in smartphone screens—capable of detecting subtle shifts in skin moisture. When a fingertip touches the sensor, it registers changes in skin capacitance, a measure of how well the skin stores electric charge, which varies with hydration levels.

The researchers suggest that this data could eventually allow people to monitor their hydration in real time—no needles, wearables, or lab work required. A quick touch could alert someone to drink water or replenish fluids before symptoms like dizziness or fatigue begin to set in.

“We envision real-time, everyday, user-friendly hydration monitoring, where users simply place their finger on their smartphone screen to assess their hydration status,” says study author Soumia Siyoucef, a former visiting student in Al-Naffouri’s research group.

To validate their technology, the KAUST team collected more than 4,000 fingertip readings from people either observing Ramadan and fasting much of the day or athletes engaged in a game of ultimate Frisbee or working out at the gym. They trained machine-learning models to convert small changes in skin conductance into a measure of the body’s water content.

When put to the test, the system delivered impressive results—accurately distinguishing between hydrated and dehydrated states up to 92% of the time among athletes and 87% among fasting individuals.