Maintaining bodily water balance is essential for survival. Although sweat serves as a key indicator of physical and mental health, existing wearable technologies can only monitor substantial sweat volumes.

To overcome this limitation, researchers conducted a new study and developed a lightweight (1 g), thin (1 mm thick) wearable patch that is attachable to the skin. This patch is capable of accurately measuring trace amounts of insensible perspiration, which refers to the water vapor that evaporates from the body surface even during rest. The findings are published in the journal Advanced Science.

The patch’s channels, comprising sponges made from a superhydrophilic polymer, emulate the water absorption mechanisms observed in plants. This design facilitates the rapid and reliable monitoring of trace sweat amounts. Additionally, the sweat entering the channels is colored using a food dye to visually confirm the volume and rate of perspiration, thus indicating the state of dehydration.