Wearable sweat-analysing sensors connected to a smartphone app have been developed by American researchers, hailing a major breakthrough in real-time health monitoring.
The sensors, described in the latest issue of the journal Nature, can pick up some key chemicals and metabolites present in human sweat and indicate whether the person is suffering from health issues such as dehydration, fatigue or high body temperature.
"Human sweat contains physiologically rich information, thus making it an attractive body fluid for non-invasive wearable sensors," said Ali Javey, a professor of electrical engineering and computer sciences at the University of California, Berkeley, who led the research.
"However, sweat is complex and it is necessary to measure multiple targets to extract meaningful information about your state of health. In this regard, we have developed a fully integrated system that simultaneously and selectively measures multiple sweat analytes, and wirelessly transmits the processed data to a smartphone.”
The device is a major step forward from currently existing fitness and health monitors that can only measure parameters such as heart rate.
Javey’s team closely cooperated with Berkeley’s exercise physiologist George Brooks to understand the chemistry of sweat and what indicators it can give about human health.
"When studying the effects of exercise on human physiology, we typically take blood samples,” Brooks said. “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 team has packed five sensors into the flexible prototype circuit board that measure glucose, lactate, sodium and potassium, as well as skin temperature.
"The integrated system allows us to use the measured skin temperature to calibrate and adjust the readings of other sensors in real time," said Wei Gao from Javey’s team. "This is important because the response of glucose and lactate sensors can be greatly influenced by temperature."
The data from the sensors is wirelessly transmitted through 10 integrated off-the-shelf circuit chips. A specially developed smartphone app then analyses the data and provides information to the user.
The technology could be embedded into various health tracking devices including smart wristbands and headbands.
"We can easily shrink this device by integrating all the circuit functionalities into a single chip," said Sam Emaminejad, a postdoc researcher at Javey’s lab. "The number of biochemicals we target can also be ramped up so we can measure a lot of things at once.”
The technology could be used to monitor the performance of athletes and other professionals that work under high levels of physiological stress. In the future, similar sensors could be used to analyse not only sweat but other types of body fluid and provide real-time data on the condition of patients recovering from illnesses and injuries.
The researchers tested the technology on several dozen volunteers that have been put through exercise sessions of various duration and intensity.