Fluidic Patch Device to Sample Sweat for Accurate Measurement of Sweat Rate and Chemical Composition: A Proof-of-Concept Study

Abstract

Sweat sensors that can continuously sample sweat are critical for determining the time-dependent physiological responses occurring in normal daily life. Here, a new device, termed fluidic patch, for collecting human sweat samples at defined time intervals is developed, and the proof-of-concept is demonstrated. The device comprises micropumps and a disposable microfluidic patch attached to the human skin. The fluidic patch continuously collects aliquots of freshly secreted sweat accumulated in the fluidic pathway at accurately defined time windows (typically 5 min). By measuring the weight of the collected samples, the local sweat rate is calculated. The sweat sample collected can be directly subjected to a wide range of chemical analyses. For the proof-of-concept, we compared the sweat rates during passive heating in human trials using the fluidic patch and the conventional ventilated sweat capsule system. Although the sweat rate obtained using the fluidic patch highly correlated with that of the ventilated sweat capsule (R 2 = 0.96, y = 1.4x – 0.05), the fluidic patch overestimated the sweat rate compared with the ventilated capsule system when the sweat rate exceeded 0.5 mg/(cm2·min). The sampled sweat was analyzed for sodium, potassium, chloride, lactate, pyruvate, and cortisol. The device could obtain the time courses of the concentrations of the abovementioned three ions; the concentrations of sodium and chloride increased linearly with the sweat rate during passive heating (R 2 = 0.76 and 0.66, respectively). The device can reliably measure the sweat rate and collect sweat samples for chemical analysis. It can be utilized for real-time physiological investigations toward wider applications.

Multiplex Chroma Response Wearable Hydrogel Patch: Visual Monitoring of Urea in Body Fluids for Health Prognosis

“…The sweat was also collected for determination using high-performance liquid chromatography tandem mass spectrometry (HPLC–MS/MS), the method of sweat collection was in accordance to a previously reported procedure. We taped several non-woven dressings with high water absorption capacity on the volunteers’ skin. − These dressings are taped around the urea sensing patch and are used to absorb and collect sweat from the volunteers. The collected sweat was diluted four times with deionized water for HPLC analysis to compare with the detection readings of the urea sensing patch.…”

Low-Cost Wearable Fluidic Sweat Collection Patch for Continuous Analyte Monitoring and Offline Analysis

“…Ohashi et al recently presented a new sweat collection system with micropumps for chronological sweat sampling, which proved to collect a sample approximately every 5 min. 49 Although a larger sequence of samples can be collected, samples are highly diluted (typically four times) and the sampling requires a strict protocol during the tests.…”

“…However, because they used the labor-intensive absorbent patch method and they used a different physiological protocol, the number of samples that were collected over time were limited to 1 for every 10–12.5 min. Ohashi et al recently presented a new sweat collection system with micropumps for chronological sweat sampling, which proved to collect a sample approximately every 5 min . Although a larger sequence of samples can be collected, samples are highly diluted (typically four times) and the sampling requires a strict protocol during the tests.…”

Foxa1 mediates eccrine sweat gland development through transcriptional regulation of Na-K-ATPase expression

“…There are several sodium-potassium pumps in the folds created by the cell membrane in the secretory region of the human exocrine sweat glands, which supply the driving force for the sodium-potassium-chloride transporter ( 26 - 28 ). Emerging evidence shows that the Na + /K + -ATPase marker is one of the sweat gland-specific markers ( 29 , 30 ).…”