Soft, skin-interfaced microfluidic systems with integrated immunoassays, fluorometric sensors, and impedance measurement capabilities

Sungbong Kim; Boram Lee; Jonathan T. Reeder; Seon Hee Seo; Sung-Uk Lee; Aurélie Hourlier-Fargette; Joonchul Shin; Yurina Sekine; Hyoyoung Jeong; Yong Suk Oh; Alexander J. Aranyosi; Stephen P. Lee; Jeffrey B. Model; Geumbee Lee; Min-Ho Seo; Sung Soo Kwak; Seongbin Jo; Gyungmin Park; Sunghyun Han; Inkyu Park; Hyo-Il Jung; Roozbeh Ghaffari; Jahyun Koo; Paul V. Braun; John A. Rogers

doi:10.1073/pnas.2012700117

Edited by Klavs F. Jensen, Massachusetts Institute of Technology, Cambridge, MA, and approved September 25, 2020 (received for review June 18, 2020)

Significance

Skin-interfaced, wireless devices for clinical-grade monitoring of physiological parameters are of growing interest for uses that range from healthcare to sports performance. This paper introduces a multifunctional skin-mounted microfluidic platform for capture and biomarker analysis of microliter volumes of sweat, a biofluid that can be collected noninvasively, with potential relevance in biophysical sensing. The focus is on colorimetric and digital assessments of a collection of parameters related to stress, including concentrations of vitamin C, cortisol, and glucose, along with quantitative measurements of sweat rate and galvanic skin response. The results represent important additions to a portfolio of emerging capabilities in skin-interfaced technologies for physiological monitoring, with particular relevance to conditions that follow from unhealthy levels of physical and mental stress.

Abstract

Soft microfluidic systems that capture, store, and perform biomarker analysis of microliter volumes of sweat, in situ, as it emerges from the surface of the skin, represent an emerging class of wearable technology with powerful capabilities that complement those of traditional biophysical sensing devices. Recent work establishes applications in the real-time characterization of sweat dynamics and sweat chemistry in the context of sports performance and healthcare diagnostics. This paper presents a collection of advances in biochemical sensors and microfluidic designs that support multimodal operation in the monitoring of physiological signatures directly correlated to physical and mental stresses. These wireless, battery-free, skin-interfaced devices combine lateral flow immunoassays for cortisol, fluorometric assays for glucose and ascorbic acid (vitamin C), and digital tracking of skin galvanic responses. Systematic benchtop evaluations and field studies on human subjects highlight the key features of this platform for the continuous, noninvasive monitoring of biochemical and biophysical correlates of the stress state.

Footnotes

↵¹S.K., B.L., J.T.R., and S.H.S. contributed equally to this work.
↵²Present address: Phil and Penny Knight Campus for Accelerating Scientific Impact, University of Oregon, Eugene, OR 97403.
↵³To whom correspondence may be addressed. Email: rooz{at}northwestern.edu, jahyunkoo{at}korea.ac.kr, pbraun{at}illinois.edu, or jrogers{at}northwestern.edu.

Author contributions: S.K., B.L., J.T.R., S.H.S., R.G., J.K., P.V.B., and J.A.R. designed research; S.K., J.T.R., S.H.S., S.-U.L., A.H.-F., J.S., H.J., Y.S.O., G.L., M.-H.S., S.S.K., S.J., G.P., S.H., I.P., H.-I.J., and J.K. performed research; S.K., B.L., J.T.R., J.S., Y.S., H.J., Y.S.O., A.J.A., S.P.L., J.B.M., G.L., M.-H.S., S.S.K., I.P., H.-I.J., R.G., J.K., P.V.B., and J.A.R. contributed new reagents/analytic tools; S.K., B.L., S.H.S., S.-U.L., A.H.-F., J.S., Y.S., Y.S.O., A.J.A., S.P.L., J.B.M., G.L., M.-H.S., S.S.K., S.J., G.P., S.H., I.P., H.-I.J., R.G., J.K., P.V.B., and J.A.R. analyzed data; and S.K., B.L., J.T.R., S.H.S., A.H.-F., Y.S., Y.S.O., A.J.A., S.P.L., J.B.M., S.J., R.G., J.K., P.V.B., and J.A.R. wrote the paper.
Competing interest statement: J.A.R., J.T.R., Y.S., and S.K. are inventors on a Patent Cooperation Treaty (PCT) patent application filed by the board of trustees of Northwestern University (PCT/US2018/035661), and J.A.R., J.T.R., S.K., Y.S., and A.H.-F. are inventors on a PCT patent application filed by the board of trustees of Northwestern University (PCT/US2018/035738). R.G., A.J.A., J.B.M., S.P.L., and J.A.R. are cofounders of Epicore Biosystems Inc., which pursues commercialization of epifluidic devices.
This article is a PNAS Direct Submission.
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