Wednesday, November 23, 2016

Wearable biosensor to test sweat

Researchers has developed soft, flexible microfluidic device that easily adheres to the skin and measures the wearer’s sweat to show how his or her body is responding to exercise. A little larger than a quarter and about the same thickness, the simple, low-cost device analyzes pH and concentrations of glucose, chloride and lactate.
Credit: John A Rogers, Northwestern University

“Sweat is a rich, chemical broth containing a number of important chemical compounds with physiological health information. By expanding our previously developed ‘epidermal’ electronics platform to include a complex network of microfluidic channels and storage reservoirs, we now can perform biochemical analysis of this important biofluid,” said John A. Rogers, who led the multi-institution research team that created the ‘lab on the skin.

Rogers is the Louis Simpson and Kimberly Querrey Professor of Materials Science and Engineering, Biomedical Engineering and Neurological Surgery in the McCormick School of Engineering and Northwestern University Feinberg School of Medicine.  Rogers and his longtime collaborator Yonggang Huang are pioneers in developing skin-like stretchable electronics that move naturally with the skin, and this is their first device to monitor physiological health by analyzing biofluids.

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, a long-distance bicycle race in arid and complex conditions. The researchers placed the device on the arms and backs of the athletes to capture sweat. Details of the versatile platform for sweat analysis were published in the journal Science Translational Medicine.

During moderate or vigorous exercise, sweat winds through the tiny microscopic channels of the device and 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 brought into proximity with the device, the wireless electronics trigger an app that captures a photo of the device and analyzes the image to yield data on the biomarker concentrations.

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.)

With the long-distance cyclists, the researchers tested the durability of the device in the complex and unpredictable conditions of the desert. They found the devices to be robust: They stayed adhered to the athletes’ skin, did not leak and provided the kind of quality information the researchers sought.

Citation: "A soft, wearable microfluidic device for the capture, storage, and colorimetric sensing of sweat". Ahyeon Kohl, Daeshik Kang, Yeguang Xue, Seungmin Lee, Rafal M. Pielak, Jeonghyun Kim1, Taehwan Hwang, Seunghwan Min, Anthony Banks, Philippe Bastien, Megan C. Manco, Liang Wang, Kaitlyn R. Ammann, Kyung-In Jang, Phillip Won, Seungyong Han, Roozbeh Ghaffari, Ungyu Paik, Marvin J. Slepian, Guive Balooch, Yonggang Huang and John A. Rogers. Science Translational Medicine  23 Nov 2016: Vol. 8, Issue 366, pp. 366ra165
DOI: 10.1126/scitranslmed.aaf2593
Research funding: L’Oréal, Frederick Seitz Materials Research Laboratory at the University of Illinois at Urbana-Champaign, National Research Foundation of Korea and National Institutes of Health.
Adapted from news release by Northwestern University.
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