Monitoring the flow rate, cumulative loss and temperature of sweat can provide valuable physiological insights for the diagnosis of thermoregulatory disorders and illnesses related to heat stress. However, obtaining accurate, continuous estimates of these parameters with high temporal resolution remains challenging. Here, we report a platform that can wirelessly measure sweat rate, sweat loss and skin temperature in real time. The approach combines a short, straight fluid passage to capture sweat as it emerges from the skin with a flow sensor that is based on a thermal actuator and precision thermistors, and that is physically isolated from, but thermally coupled to, the sweat. The platform transfers data autonomously using a Bluetooth Low Energy system on a chip. Our approach can also be integrated with advanced microfluidic systems and colorimetric chemical reagents for the measurement of pH and the concentration of chloride, creatinine and glucose in sweat.
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Supporting data are available from the corresponding author upon reasonable request. Source data are provided with this paper.
Custom-developed firmware for BLE SoCs and Android applications (user interfaces) for use on smartphones are available from the corresponding author upon reasonable request. All requests for source code will be reviewed by the corresponding author to verify whether the request is subject to any intellectual property or confidentiality obligations.
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This work made use of the NUFAB facility of Northwestern University’s NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205), the MRSEC programme (NSF DMR-1720139) at the Materials Research Center, the International Institute for Nanotechnology (IIN), the Keck Foundation and the State of Illinois, through the IIN. J.U.K. and T.K. were supported by the Brain Research Program of the National Research Foundation (NRF) funded by the Korean government (MSIT; NRF-2019M3C7A1032076). J.C. acknowledges support from the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT; NRF-2019R1A2C1084419). J.A.R. acknowledge support from the National Institute on Aging of the National Institutes of Health (NIH R43AG067835). We thank the Querrey-Simpson Institute for Bioelectronics for support of this work.
J.A.R., S.L. and R.G. are cofounders and/or employees of Epicore Biosystems, Inc., a company that pursues commercialization of microfluidic devices for wearable applications.
Peer review information Nature Electronics thanks Tolga Kaya, Christopher Proctor and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Kwon, K., Kim, J.U., Deng, Y. et al. An on-skin platform for wireless monitoring of flow rate, cumulative loss and temperature of sweat in real time. Nat Electron 4, 302–312 (2021). https://doi.org/10.1038/s41928-021-00556-2