Wearable sweat sensor could monitor dehydration, fatigue

Wearable health and fitness trackers have taken the world by storm in recent years. But wristbands that monitor your heart rate and how many calories you have burned could soon be old news; researchers have now developed a device that measures sweat chemicals, which could alert users to dehydration, fatigue and more.

The wearable sweat monitor measures glucose, lactate, sodium and potassium in sweat.
Image credit: Wei Gao et al.

Ali Javey, a professor of electrical engineering and computer science at the University of California-Berkeley, and colleagues publish the details of their creation in the journal Nature.

According to the team, their non-invasive device - which can be incorporated into wristbands and headbands - is the first fully integrated electronic system that can continuously and simultaneously monitor multiple sweat chemicals.

"Human sweat contains physiologically rich information, thus making it an attractive body fluid for non-invasive wearable sensors," says Prof. Javey. "However, sweat is complex and it is necessary to measure multiple targets to extract meaningful information about your state of health."

"In this regard," he adds, "we have developed a fully integrated system that simultaneously and selectively measures multiple sweat analytes, and wirelessly transmits the processed data to a smartphone. Our work presents a technology platform for sweat-based health monitors."

Device could offer a non-invasive alternative to blood tests

The prototype device consists of a flexible circuit board containing 10 circuit chips, which is connected to five sensors that monitor glucose, lactate, sodium, potassium and body temperature.

Each of the four biochemicals measured may offer insight into the user's health and well-being. Lactate, for example, provides information on muscle fatigue, while potassium can provide information on dehydration.

On contact with sweat, the sensors generate electrical signals. These signals are read by the circuit chips and adjusted for skin temperature changes, which the researchers say is a key process.

"The integrated system allows us to use the measured skin temperature to calibrate and adjust the readings of other sensors in real time," says co-lead author Wei Gao, a postdoctoral fellow in Prof. Javey's lab. "This is important because the response of glucose and lactate sensors can be greatly influenced by temperature."

The signals are then wirelessly transmitted to a smartphone app developed by the team, which syncs the data.

Prof. Javey further explains how the device works in the video below:

The team tested the device on 26 healthy volunteers as they engaged in indoor and outdoor physical activities at different intensities, such as cycling and running. The device was incorporated into headbands and wristbands, which they wore while exercising.

Comparing the sensor readings from the device with collected sweat samples from participants, the researchers were able to confirm its accuracy and feasibility as a wearable sweat-based device that monitors health.

"The idea is to have this thumbs-up or thumbs-down device that will give real-time information: it could provide an alarm that you need to take some medication, or that you're getting dehydrated and need to drink some water," says Prof. Javey.

While blood tests are currently the "gold standard" when it comes to measuring metabolites and electrolytes in the body, study coauthor George Brooks, a professor of integrative biology at UC-Berkeley, says it has the potential to be an effective non-invasive alternative:

"Having a wearable sweat sensor is really incredible because the metabolites and electrolytes measured by the Javey device are vitally important for the health and well-being of an individual.

When studying the effects of exercise on human physiology, we typically take blood samples. With this non-invasive technology, someday it may be possible to know what's going on physiologically without needle sticks or attaching little, disposable cups on you."

The researchers note that the device could be adapted to measure other bodily fluids, providing an even deeper insight into a person's health and well-being.

"We want to develop medical applications," says Prof. Javey. "By looking at those other chemicals we may be able to get information about the mental health of an individual."

In 2014, Medical News Today reported on the creation of a wearable, skin-like device that researchers say can monitor cardiovascular and skin health 24 hours a day.