Blood tests allow doctors to peer into the human body to analyze people's health. But in the future, there may be a less invasive way to obtain valuable information about a person's health: wearable sensors that use human sweat to look for signs of disease.
Sweat is a rich source of chemical data that could help doctors determine what is happening inside the human body, scientists explained in a new study. Perspiration is loaded with molecules, ranging from simple electrically charged ions to more complex proteins, and doctors can use sweat to diagnose certain diseases, uncover drug use and optimize athletic performance, they said.
"Sweat is pretty attractive to target for noninvasive wearable sensors, since it's, of course, very easy to analyze — you don't have to poke the body to get it — and it has a lot of information about one's health in it," said study senior author Ali Javey, an electrical engineer at the University of California, Berkeley. [Bionic Humans: Top 10 Technologies]
Commercially available wearable sensors, like the Fitbit and the Apple Watch, track users' physical activities and some vital signs, such as heart rate. However, they do not provide data about a user's health on a molecular level. Now, scientists say "smart" wristbands and headbands embedded with sweat sensors could sync data wirelessly in real time to smartphones using Bluetooth.
Previously, studies of sweat largely relied on perspiration collected off the body in containers that was later analyzed in a lab. Now, researchers have devised a soft, flexible, wearable sensor array to continuously monitor changes in four molecular components of sweat and to provide real-time tracking of a person's health.
These devices might one day help athletes track their performance and enable doctors to continuously monitor the health of their patients to better personalize their medication, the scientists said.
"This could help tell athletes to take liquids or warn them they are going through heat shock," Javey told Live Science.
The invention uses five sensors to simultaneously track levels of glucose, lactate, sodium and potassium, as well as skin temperature. This data is fed to a flexible board of microchips that processes these signals and uses Bluetooth to wirelessly transmit data to a smartphone. All of these electronics could be incorporated into either a wristband or headband.
"We have a smartphone app that plots the data from sweat in real time," Javey said.
The researchers tested the device on 26 men and women who pedaled indoors on stationary bikes or ran outdoors on tracks and trails. Sodium and potassium in sweat could help check for problems such as dehydration and muscle cramps. Glucose could help keep track of blood sugar levels. Lactate levels could indicate blood flow problems, and skin temperature could reveal overheating and other problems.
In addition, the skin temperature sensor helps adjust the chemical sensors to make sure they get proper readings, the researchers said. For instance, higher skin temperatures increase the electrical signals from glucose, which can make it look as if people are releasing more glucose in their sweat than they actually are.
Previous wearable sweat monitors could track only a single molecule at a time, which could generate misleading information, the researchers said. For example, if a lone sensor showed a drop in a molecule's level, it might not be because that molecule's level is actually falling in a person's sweat, but rather because sweating has stopped, the sensor has detached from the skin or the sensor is failing. The inclusion of multiple sensors could help shed light on what is happening to a person and the sensor array as a whole.
In the near future, the researchers hope to shrink the device's electronics down and boost the number of molecules it monitors. Such molecules could include heavy metals such as lead, which recently made news for appearing in dangerously high levels in the water of Flint, Michigan, Javey noted.
In the long term, the researchers hope to conduct large-scale studies with their device on many volunteers. The data such work gathers could help researchers better understand what levels of various molecules in sweat mean for athletic performance and human health, Javey said.
The researchers have filed a patent on their work, although they are not currently collaborating with anyone to commercialize the sensors, Javey said.
The scientists detailed their findings in the Jan. 28 issue of the journal Nature.
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