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Wearable sweat biosensors offer compelling opportunities for improved personal health monitoring and non-invasive measurements of key biomarkers. Inexpensive device fabrication methods are necessary for scalable manufacturing of portable, disposable, and flexible sweat sensors. Furthermore, real-time sweat assessment must be analyzed to validate measurement reliability at various sweating rates. Here, we demonstrate a “smart bandage” microfluidic platform for cortisol detection and continuous glucose monitoring integrated with a synthetic skin. The low-cost, laser-cut microfluidic device is composed of an adhesive-based microchannel and solution-processed electrochemical sensors fabricated from inkjet-printed graphene and silver solutions. An antibody-derived cortisol sensor achieved a limit of detection of 10 pM and included a low-voltage electrowetting valve, validating the microfluidic sensor design under typical physiological conditions. To understand effects of perspiration rate on sensor performance, a synthetic skin was developed using soft lithography to mimic human sweat pores and sweating rates. The enzymatic glucose sensor exhibited a range of 0.2 to 1.0 mM, a limit of detection of 10 μM, and reproducible response curves at flow rates of 2.0 μL min −1 and higher when integrated with the synthetic skin, validating its relevance for human health monitoring. These results demonstrate the potential of using printed microfluidic sweat sensors as a low-cost, real-time, multi-diagnostic device for human health monitoring.
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Moisture Based Perspiration Level Estimation
Perspiration level monitoring enables numerous applications such as physical condition estimation, personal comfort monitoring, health/exercise monitoring, and inference of environmental conditions of the user. Prior works on perspiration (sweat) sensing require users to manually hold a device or attach adhesive sensors directly onto their skin, limiting user mobility and comfort. In this paper, we present a low-cost and novel wearable sensor system that is able to accurately estimate an individual's sweat level based on measuring moisture. The sensor is designed in a threadlike form factor, allowing it to be sewn into the seams of clothing, rather than having to act as a standalone sensor that the user must attach to their body. The system is comprised of multiple cotton-covered conductive threads that are braided into one sensor. When a person sweats, the resistance between the braided conductive threads changes as moisture becomes trapped in the cotton covering of the threads. The braided three-dimensional structure allows for robust estimation of perspiration level in the presence of external forces that may cause sensor distortion, such as motion. We characterize the relationship between the volume of sweat and measured resistance between the braided threads. Finally, we weave our sensors into the fabric of a shirt and conduct on-body experiments to study users' sweating level through various activities.
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- PAR ID:
- 10230938
- Date Published:
- Journal Name:
- Proceedings of the 2018 ACM International Joint Conference and 2018 International Symposium on Pervasive and Ubiquitous Computing and Wearable Computers
- Page Range / eLocation ID:
- 1301 to 1308
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1145/3267305.3274177
