In the future, athletic trainers may be able to gauge hydration levels, pH levels, and other variables just from monitoring athletes’ sweat. Or at least that’s the goal, according to researchers at Purdue University and Northwestern University who have developed two different sweat-measuring wearables.
The team at Purdue has created a skin patch that changes color as hydration levels shift. An article from SportTechie explains that the patches are made from laser-machinated filter paper with water-impermeable film strips. The patch’s strips create microchannels that have a water-activated dye. As the level of sweat increases, the strips’ color changes from blue to red. As a result, the amount of moisture that is lost is easily identified.
“We can do something very simple just by changing color based on hydration. It’s just a matter of putting sensors on paper,” Babak Ziaie, PhD, a Professor of Electrical and Computer Engineering at Purdue, told the Big Ten Network. “I like simple solutions for problems. I think it has to be simple for it to be adapted.”
Testing results reveal that Purdue’s patch can be used for approximately 15 to 90 minutes, with a standard rate of sweating 90 microliters per hour within a square centimeter of skin. This rate was aligned with standard rates of sweating for most people.
“Hydration in humans is a delicate parameter,” Dr. Ziaie said in a university statement. “Even small deviations such as two percent from normal levels can affect a person’s cognitive and physical performance by more than 30 percent.”
An application for a patent has been filed by the Purdue researchers. They say the patch can be manufactured easily, and it has garnered interest from a variety of fields.
“In comparison [to conventional methods for monitoring hydration], our approach is a fast, user-friendly dermal patch for collecting and measuring sweat secretion,” Dr. Ziaie said. “And our fabrication process could be scaled up to large-volume manufacturing.”
“We have talked to many experts, including marathon directors, the Ironman World Championship, Olympic triathlon athletes, and many collegiate and professional coaches, athletes, race directors, and EMTs to validate the need for this kind of product,” echoed Vaibhav Jain, a graduate student at Purdue, in a statement. “Also, two industrial companies have shown interest in our technology, and we are in talks with them.”
At Northwestern, a team of researchers has recently published work on a different wearable product that monitors sweat. This device is designed to measure pH acidity and lactose and chloride levels, among other variables.
“We don’t refer to it as a ‘patch,’ because that connotes a fabric,” John Rogers, PhD, Material Sciences and Engineering Professor at Northwestern, told the Big Ten Network. “This is latex-like and embeds these channels. We’re able to measure these biomarkers but also able to quantify sweat loss and sweat rate. There are so many things you can do with that technology. It’s the next generation of wearables.”
In terms of its composition, Northwestern's device is more skin-like than most patches. Dr. Rogers’ team has partnered with a number of outside organizations to develop the product with hopes of moving it forward for consumers.
“To get things into the commercial world, we typically do startups and could work with them,” Dr. Rogers said. “The technology works. We’ve had at least 100 to 200 devices tested in the field. By comparison to the technical maturity of other engineering advances, we’re way down the road in terms of getting it ready. We’ve done it before, so it’s nothing [terribly] new. But if all we do is publish a paper, we feel like we’ve fallen short.”