Scientists at the University of California, Berkeley, are developing wearable skin sensors that can detect the elements in the sweat. This discovery is expected to replace the need for invasive procedures like blood tests for which blood is drawn, by monitoring the perspiration. The procedure can provide real-time updates on health-related problems such as dehydration and fatigue.
The team of scientists has described a new sensor design which is easy to manufacture using a “roll-to-roll” technique used for processing that efficiently prints the sensors on sheets of plastic. The sensors are used to monitor the perspiration rate and the metabolites and electrolytes in sweat. Samples of the sweat were taken from some volunteers who were excising and others who were experiencing chemically induced perspiration.
“The goal of the project is not just to make the sensors but start to do many subject studies and see what sweat tells us — I always say ‘decoding’ sweat composition,” said Ali Javey, a professor of electrical engineering and computer science at UC Berkeley and senior author on the paper.
“For that, we need sensors that are reliable, reproducible, and that we can fabricate to scale so that we can put multiple sensors in different spots of the body and put them on many subjects,” said Javey, who is also a faculty scientist at Lawrence Berkeley National Laboratory.
The newly manufactured sensors contain a spiraling microscopic tube, or microfluidic, that absorbs sweat from the skin. The sensors track the movement of the sweat through the microfluidic. The sensors are capable of reporting how much a person is sweating and their sweat rate. The microfluidics also contains chemical sensors that can detect concentrations of electrolytes like sodium and potassium and metabolites like glucose.
Test and the result.
The team of scientists worked in a collaboration with the researchers at the VTT Technical Research Center of Finland to come up with a fast way to manufacture the sensor patches in a roll-to-roll technique similar to screen printing.
“Roll-to-roll processing enables high-volume production of disposable patches at low cost,” Jussi Hiltunen of VTT said. “Academic groups gain significant benefit from roll-to-roll technology when the number of test devices is not limiting the research. Additionally, up-scaled fabrication demonstrates the potential to apply the sweat-sensing concept in practical applications.”
To test the sensors, the researchers placed the sweat sensors on different parts of the volunteer’s bodies including the forehead, forearm, underarm and upper back. Then they measured their sweat rates and the level of sodium and potassium in the sweat while they rode an exercise bike. The researchers found that sweat rates indicate the body’s overall liquid loss during exercise, which means that tracking sweat rate might give athletes an early indication when they are over-exercising and exerting themselves.
“Traditionally what people have done is they would collect sweat from the body for a certain amount of time and then analyze it,” said Hnin Yin Yin Nyein, a graduate student in materials science and engineering at UC Berkeley and one of the lead authors on the paper. “So you couldn’t really see the dynamic changes very well with good resolution. Using these wearable devices we can now continuously collect data from different parts of the body, for example, to understand how the local sweat loss can estimate the whole-body fluid loss.”