While participating in last year's El Tour de Tucson, a competitive long-distance bicycle race, more than a dozen volunteers were simultaneously participating in and conducting a real-world scientific study, one that involved a diminutive device that rapidly and painlessly analyzes body chemistry from sweat.
Among the volunteers were faculty and students at the University of Arizona and the University of Illinois who helped develop a first-of-its-kind soft, stretchable wearable microfluidic sweat sensor. The device is applied and directly adheres to the skin and measures biomarkers in the wearer’s sweat to reveal information regarding internal chemistries, loss of electrolytes, fluid status and the overall body's response to exercise.
A little larger than a quarter and about the same thickness, the simple, low-cost device helps the wearer quickly decide if any adjustments, such as drinking more water or replenishing salts, electrolytes and sugar, need to be made or if something is medically awry.
Designed for one-time use of a few hours, the device, placed directly on the skin of the forearm or back, also can detect the presence of a biomarker for cystic fibrosis. Such wearable microfluidic devices may be adapted and used in the future for disease diagnosis and therapeutic monitoring.
"We wanted to rapidly and painlessly obtain information, without needles, about the body's internal milieu," said cardiologist and co-investigator Dr. Marvin J. Slepian, director of the Arizona Center for Accelerated Biomedical Innovation, or ACABI, at the University of Arizona Health Sciences. "Sweat contains numerous chemical compounds that point to the status of one's health, and this device allows us to examine medically relevant biomarkers, including sodium, potassium, lactate, glucose and pH, without the invasiveness of a blood draw."
Northwestern University's John A. Rogers led the multi-institution research team that created the device. Rogers is the director of Northwestern’s Center for Bio-Integrated Electronics. The Slepian lab and ACABI have been long-standing collaborators with Rogers in developing novel wearable, stretchable electronic systems for human and medical use.
The sweat analysis platform contains integrated electronics that require no battery but enable wireless connection to a smartphone.
Details of the versatile platform for sweat analysis were published Nov. 23 by the journal Science Translational Medicine.
In a study of accuracy and durability, the device was tested on two different groups of athletes: one cycling indoors in a fitness center under controlled conditions and the other participating in the El Tour de Tucson in arid conditions. The researchers placed the device on the arms and backs of the athletes, including Slepian, to capture sweat.
In the group that cycled indoors, the researchers compared the new device’s biomarker readouts to conventional laboratory analysis of the same sweat and found the two sets of results agreed with each other. Conventional methods include capturing sweat with absorbent patches taped to the skin and analyzing them off-site, not in real time.
With the long-distance cyclists, the researchers tested the durability of the device in the complex and unpredictable conditions of the desert and found them to be robust. They stayed adhered to the athletes’ skin, did not leak and provided the kind of quality information the researchers sought.
“Once we put on the device, we did not even know we had it on during the race,” Slepian said. “On the other hand, we got a handle over the six-hour event as to how we were losing critical electrolytes, and we made adjustments to our intake of fluid and sports drink.”
During moderate or vigorous exercise, sweat moves through the tiny microscopic channels of the device into four different small, circular compartments. In the compartments, reactions with chemical reagents result in visible color changes in ways that quantitatively relate to pH and concentrations of glucose, chloride and lactate.
When a smartphone is placed near the device, wireless electronics trigger an app that captures a photo of the device and analyzes the image to yield data on biomarker concentrations.
The device also can determine sweat rate and loss, and it can store samples for subsequent laboratory analysis, if necessary.
The multidisciplinary work involved close collaborations with clinical investigators, including Slepian, also a UA professor of medicine and biomedical engineering, the McGuire Scholar in the Eller College of Management and a member of the UA Sarver Heart Center, as well as contributions from dermatology experts from L’Oréal, including Guive Balooch. Slepian and Balooch are co-authors of the study. L’Oréal; the Frederick Seitz Materials Research Laboratory at the University of Illinois, Urbana-Champaign; the National Research Foundation of Korea; and the National Institutes of Health (grant R01EB019337) supported the research.
The title of the Science Translational Medicine paper is “A Soft, Wearable Microfluidic Device for the Capture, Storage and Colorimetric Sensing of Sweat.”
Other institutions with authors on the paper are the University of Illinois, Urbana-Champaign; Ajou University, Korea; Hanyang University, Korea; Zhejiang University, China; and MC10 Inc.