Engineering news
The molecules in sweat can carry as much information as the blood, and wearable sweat sensors are currently used to test for cystic fibrosis, measure glucose levels in diabetics, and even to determine how much alcohol someone has consumed.
But for them to work, the subject has to sweat – which means turning up the temperature to stifling levels, or having them run on a treadmill. If you want to measure how levels of a particular substance in the sweat change over time, that means a lot of running, and an uncomfortable experience for patients.
The new device, developed by a team at the University of Cincinnati, will allow researchers and medics to analyse their subjects’ sweat without turning up the heat or making them run on a treadmill.
The device uses a combination of a chemical stimulant and an electrical current to produce sweat, even when the patient is relaxed and cool. In their trial, which was published in the journal Lab on a Chip, the researchers applied a gel containing carbachol – a chemical used in eyedrops – to their subject’s forearm.
Then, an electrical current of 0.2 milliamps drives a tiny amount of carbachol into the upper layer of the skin, stimulating sweat glands without causing any physical sensation or discomfort. The method could induce sweating under the sensor for as long as five hours.
Jason Heikenfeld, a professor at the University of Cincinnati, said there were a number of applications in medicine and beyond. “Imagine being able to monitor cardiac patients after they have been released from the hospital, or preventing dehydration in athletes or even helping ensure that your body is getting the exact right concentrations of a prescription drug,” he continued.
Zachary Sonner, a lead author on the paper, said the device would open up more portable tests of sweat – in patients recovering from surgery at home, for example. “The end goal is to take the idea from a benchtop test to a portable device – perhaps for people in high-stress jobs like airline pilots – and analyze them for stress,” he said. "If you're a pilot, you can't do blood draws while you're flying the plane. But a sensor could analyze sweat so we can begin to understand how their body responds to stressful situations.”
“The challenge is not only coming up with new technological breakthroughs like this, but also bringing all these technology solutions together in a reliable and manufacturable device,” said Heikenfeld.
He has co-founded a company, Eccrine Systems, that will seek to tap into the growing biosensors market. The industry is valued at $88bn in the United States, and is poised to see explosive growth in the next five years, according to market research firm IbisWorld.