A lot of sweat, quite literally, has gone into the development of a breakthrough wearable monitor that can alert users to health problems such as dehydration and fatigue.
The device contains five sensors that measure skin temperature and four chemicals in human sweat to track changes in the wearer’s physiology.
The US researchers behind the technological leap, published in the journal Nature, believe the device could be used in the future to track health trends in community-wide studies and for applications such as monitoring medical drug use.
Lead researcher Professor Ali Javey of the University of California, Berkeley, said the sweat-based sensor was an advance on health monitors currently on the market.
“The products that are in the market today monitor the heart rate and pulse rate, but they don’t provide any information about the composition of body fluids like sweat that can give certain information about what is happening with your health,” he said.
Dr Javey said sweat analysis was already used for applications such as disease diagnosis, drug abuse detection and athletic performance optimisation.
However, while sweat is rich in physiological information, it has been difficult to collect and analyse.
“You had to get somebody to bike quite a bit, sweat quite a lot — maybe 10 millilitres — and collect that sweat using a cup and then send that sweat for analysis to a different lab,” he said.
Device could pinpoint warning signs of disease
Dr Javey said sweat-based sensors were not a new innovation but until now they had been able to screen only one chemical.
“Sweat is complex and it is necessary to measure multiple [chemicals] to extract meaningful information about your state of health,” he said.
Dr Javey’s team overcame this hurdle through a device that includes five sensors and a flexible circuit board for signal processing and wireless transmission of data.
The sensors stick to the skin and measure skin temperature and four chemicals in the sweat: sodium, potassium, glucose and lactate.
To confirm the accuracy of the device, the research team monitored 26 volunteers while they exercised using both the prototype and lab analysis of collected sweat samples.
Dr Javey said the study had shown the “sensors can provide information about whether the user is undergoing dehydration or muscle fatigue”.
However he also believed the device had the potential to deliver personalised and community-wide health information.
“What we are excited about is we can use the platform [we have developed] and modify it for different chemicals. It’s very easy and comfortable to wear and you don’t need to sweat much for the sensors to activate.”
This would allow for large population studies that could help pinpoint predictive markers of disease and increase understanding of the health status and clinical needs of individuals and society, he added.
While the technology was currently dependent on the user working up a sweat, Dr Javey said his team were already looking at ways it could monitor physiological conditions while people were sedentary, for example sitting at a desk.
‘Real leap forward for wearable devices’
In an opinion piece accompanying the study, Dr Jason Heikenfeld from the University of Cincinnati described the development as a “real leap forward for wearable devices”.
“Today’s commercially available wearables largely rely on decades-old technology. Their market success is due to a convergence of improved affordability and ergonomics and a rapidly growing consumer awareness of health,” Dr Heikenfeld wrote.
He said the potential applications of wearable sweat-sensing devices extended well beyond those related to exercise.
“For example, the hormone cortisol is a marker of stress, and its concentrations in sweat are similar to those found in blood, making it a possible target for future monitoring.”
“Even small-molecule drugs and their metabolites come out in sweat, so this body fluid might one day be used to monitor the amount of active drug in a patient’s blood — helping to avoid rises and falls in drug levels between doses.”