Researchers in Korea have developed a sweat sensor that they say can “heal” itself if damaged during exercise.

It can also measure electrolyte levels in sweat. Like the other biochemical markers contained in sweat — metabolites and heavy metals — electrolytes can provide insights into the wearer’s health. But available sweat sensors, including patches, bandages and tattoos, can be impaired by natural movements such as walking, running, throwing or jumping. If the sensors are scratched or broken during exercise, they often cannot be repaired.

Sung Yeon Hwang, Jeyoung Park, Bong Gill Choi and colleagues wanted to develop a wearable sweat sensor that could withstand vigorous exercise and quickly repair itself if damaged. The researchers recently reported in ACS Applied Materials & Interfaces, that they have developed a headband that measures electrolyte levels in sweat  — and can repair itself if damaged.

To make their self-healing sensor, the researchers coated carbon fiber thread electrodes with a citric acid-based polymer. When cut, the threads quickly rejoined through hydrogen bonding of the polymer. They sewed the threads, which could detect potassium and sodium ions, into a headband and added a wireless electronic circuit board that could transfer data to a smart phone. A human volunteer wore the headband while exercising on a stationary bike, and the sensor accurately tracked the electrolyte concentrations in their sweat over 50 minutes of exercise. During cycling, the researchers cut the sensor threads with scissors, and the threads healed and returned to normal operation in only 20 seconds.

You can watch a video of the self-healing sweatband here.