Single‐use paper‐based wearable devices are receiving increasing attention as a novel platform for disposable, inexpensive, noninvasive, and real‐time sweat monitoring. The bidirectional liquid transport nature of paper is the most critical barrier to effectively controlling sweat samples for reliable and accurate sweat analysis. Excessive or additionally released sweat significantly interferes with analysis when mixed with old sweat. Moreover, bio‐receptors pre‐loaded in the sensing areas can backflow and move to another sensing region generating a cross‐talk issue. This work enables effective sweat sampling and delivery in paper by facilitating unidirectional sweat transport from the skin to the sensing reservoir. The design and fabrication of a single‐layered paper membrane to achieve Janus‐type properties, which only allow moisture to flow in one direction is introduced. When the hydrophobic side of the Janus paper is placed on the skin, sweat is unidirectionally self‐pumped from the hydrophobic side to the hydrophilic sensing areas, but not the reverse. The fabrication takes two steps including easy automatic and scalable printing of hydrophobic micropatterns on paper and simple heating of the printed paper for the wax penetration. Quantitative colorimetric assessment of pH, chloride, sodium, and glucose in sweat is simultaneously performed without cross‐talk between the sensing regions.
The erratic, intermittent, and unpredictable nature of sweat production, resulting from physiological or psychological fluctuations, poses intricacies to consistently and accurately sample and evaluate sweat biomarkers. Skin‐interfaced microfluidic devices that rely on colorimetric mechanisms for semi‐quantitative detection are particularly susceptible to these inaccuracies due to variations in sweat secretion rate or instantaneous volume. This work introduces a skin‐interfaced colorimetric bifluidic sweat device with two synchronous channels to quantify sweat rate and biomarkers in real‐time, even during uncertain sweat activities. In the proposed bifluidic‐distance metric approach, with one channel to measure sweat rate and quantify collected sweat volume, the other channel can provide an accurate analysis of the biomarkers based on the collected sweat volume. The closed channel design also reduces evaporation and resists contamination from the external environment. The feasibility of the device is highlighted in a proof‐of‐the‐concept demonstration to analyze sweat chloride for evaluating hydration status and sweat glucose for assessing glucose levels. The low‐cost yet highly accurate device provides opportunities for clinical sweat analysis and disease screening in remote and low‐resource settings. The developed device platform can be facilely adapted for the other biomarkers when corresponding colorimetric reagents are exploited.
more » « less- NSF-PAR ID:
- 10482509
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Science
- Volume:
- 11
- Issue:
- 10
- ISSN:
- 2198-3844
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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