Wearable sensor measures skin hydration

Engineers from North Carolina State University have created a wearable sensor for measuring skin hydration, which has a range of potential medical and lifestyle applications.

(Credit: Shanshan Yao)
(Credit: Shanshan Yao)

Described in the journal Advanced Healthcare Materials, the sensor consists of two elastic polymer composite electrodes that contain conductive silver nanowires. Skin’s electric properties change in relation to its hydration, and it’s these changes that the electrodes measure.

“We have developed technology that allows us to track an individual’s skin hydration in real time,” said Yong Zhu, an associate professor of mechanical and aerospace engineering at NC State and co-author of the paper.

“Our sensor could be used to protect the health of people working in hot conditions, improve athletic performance and safety, and to track hydration in older adults or in medical patients suffering from various conditions. It can even be used to tell how effective skin moisturisers are for cosmetics.”

The researchers tested the sensor in the lab on a variety of artificial skins. They claim their inexpensive prototypes – which cost about one dollar – were just as accurate as a large commercial hydration monitor that operates on a similar principle.

The team also embedded their sensors in two wearable devices: an adhesive patch for the chest and a wristwatch. Both devices were able to accurately relay data wirelessly to a computer, smartphone or tablet, opening up the possibility of third parties such as doctors monitoring hydration levels.

“It’s difficult to measure a person’s hydration quantitatively, which is relevant for everyone from military personnel to athletes to firefighters, who are at risk of health problems related to heat stress when training or in the field,” said John Muth, a professor of electrical and computer engineering at NC State and another co-author of the work.