A new wearable microfluidic sweat analytics system measures sweat and sweat biomarkers. It is a soft, flexible device that measures the bodies’ response to exercise. Northwestern University professor John A. Rogers is collaborating with a broad collection of partners to bring his microfluidic device into widespread distribution.

The device measures sweat and sweat biomarkers accurately and in real time, allowing athletes, military personnel, fitness pros and others to monitor sweat rate and electrolyte loss, so they can keep hydrated, replenish their electrolytes and stay on top of their game.

Previously developed in Rogers' Northwestern Engineering laboratory, the soft, flexible device sits on the skin and measures sweat to determine how the body responds to exercise. It has plans to co-package them with nutritional, skin health, cosmetics and sports hydration products, with additional possibilities for use in clinical medicine and rehabilitation.

"Through our partnership with Epicore Biosystems, we're developing exciting new ways to measure and monitor sweat, which can help us better recommend hydration strategies for our athletes," said Dr. Lindsay Baker, principal scientist at the Gatorade Sports Science Institute.

Earlier microfluidic designs measured chloride loss, glucose, lactate and pH levels in sweat. Newer platforms also quantify concentrations of heavy metals such as lead and arsenic and urea and creatinine levels, the latter of which relates to kidney health.

"The devices from a year ago could determine the average chloride concentration during an exercise period," Rogers said. "But now we have devices that fill sequentially in time. This is important because variations in sweat biomarkers give a sense of fatigue level as you're exercising. We didn't have that capability previously."

Athletes can monitor these sequentially changing levels with a simple glance. During exercise, sweat winds its way through the device's microscopic channels and into different compartments. In those compartments, reactions with chemical reagents result in visible color changes that quantitatively relate to electrolyte concentrations.

Another unique feature of these latest platforms is their ability to measure users' sweat during aquatic sports, even when fully underwater. New adhesive materials and microfluidic designs maintain water-tight seals to the skin to capture and analyze sweat while preventing surrounding water from entering the device's microscopic channels.

"Skin-mounted microfluidic devices from the Rogers group allow us, for the first time, to determine sweat and electrolyte loss continuously," said Jarod Schroeder, head coach of Northwestern's men's swimming team. 'The insights are intriguing. The remarkably high levels of sweat loss that occur in the pool demand careful scheduling for rehydration."

"These thin, flexible microfluidic networks allow us to quantitatively track sweat loss and sweat chemistry across players in our organization," said Lorena Martin, the Mariners' director of high performance. "These data can provide us with unique, detailed, player-specific information on electrolyte balance and body chemistry at any point during a game or practice."

"Sweat is rich in biochemical information that is relevant to physiological health and cognitive state," said Jennifer Martin, a research chemist at the Air Force Research Laboratory.

Patients also are using the devices at Shirley Ryan AbilityLab. Researchers there are exploring left/right asymmetries in sweating as a metric for recovery in stroke patients. The devices also help clinicians monitor differences in patients' sweat chemistry over the course of the rehabilitation process.

"The highly visual and dynamic nature of these devices allows our clinicians to readily monitor sweat loss and physical exertion in patients undergoing rehabilitation from autonomic disorders like stroke," said Arun Jayaraman, director of the Max Näder Lab for Rehabilitation Technologies and Outcomes Research at Shirley Ryan AbilityLab.

"Joining forces with science-driven organizations such as the U.S. Air Force and Gatorade will help us to deliver on a new class of wearable technology — one that provides quantitative information on sweat, with the potential to fundamentally change the way that people manage their hydration, health and performance," Ghaffari said.