A mass-customizable dermal patch with discrete colorimetric indicators for personalized sweat rate quantification

Abstract

In this paper, we present a disposable, colorimetric, user-friendly and mass-customizable dermal patch for chronological collection and discrete real-time in situ measurement of sweat secretion over a small area of skin. The patch consists of a laminated filter paper patterned into radially arranged channels/fingers with water-activated dyes at their tips. As channels are filled during perspiration, their tips change color once fully saturated, providing easily identifiable levels of water loss which in turn can be mapped to personal dehydration levels. The patch can be manufactured at low cost in a variety of sizes to allow hydration monitoring for individuals participating in activities under different conditions (intensity, temperature, humidity, etc.). Furthermore, we describe an analytical model that enables mass customization of such a flexible wearable system accommodating a broad range of sweat rates and volumes to generate patch designs that are personalized to an individual’s sweat rate, desired time of usage, and the temporal resolution of the required feedback. As a proof-of-concept demonstration, we characterized laser-fabricated patches that cover (7 cm × 5 cm) area of skin having various wicking materials, thicknesses (180–540 µm), and pore sizes (3–11 µm). Tests were conducted at various flow rates simulating different sweating intensities in the range of 1.5–15 mg/cm 2 /min. Experimental results for the case of a half-marathon runner targeting 90 min of usage and sweating at a rate of 1.5 mg/cm 2 /min indicated measurement accuracy of 98.3% when the patch is completely filled.

Wearable Sweat Loss Measuring Devices: From the Role of Sweat Loss to Advanced Mechanisms and Designs

“…Unfortunately, the development of wearable sweat biosensors faces some obstacles about sweat rate, such as complex flow-rate-dependent concentration of sweat components, low accuracy of measurement to evaluate known The significance of measuring two types of sweat loss and summary of wearable sweat loss measuring devices based on hygrometer (open chamber method and closed chamber method), absorbent materials (paper: Reproduced with permission. [33] Copyright 2019, Springer Nature, sponge: Reproduced with permission. [34] Copyright 2014, John Wiley & Sons, textile: Reproduced with permission.…”

Thread-based multiplexed sensor patch for real-time sweat monitoring

“…The measurements provide an instantaneous value of the concentration of analyte in sweat, and does not account for the sweat rate, which can vary over an order of magnitude across subjects. One could utilize one of the published methods to measure sweat rate based on capillary action in future work 28,29 . The selectivity of sweat sensors especially ion-selective electrodes is very important as sweat contains various electrolytes of similar charge and size.…”

Molecular and physical technologies for monitoring fluid and electrolyte imbalance: A focus on cancer population

“…23 Skin patch for measuring sweat rate and hydration status (adapted from Ref. [24]). Mucosal dryness in dehydrated patients using an oral moisture-checking device (Mucus R , Life Co. Ltd.) (adapted from Ref.…”

“…Stable isotope labeling is a more commonly used technique, and Figure 6B shows a typical schematic representation of a human subject participating in an isotope tracer infusion. The sample with the known concentration of isotopes (usually nonradioactive, deuterium ( 2 H), deuterium oxide ( 2 H 2 O), or oxygen-18 ( 18 O)); rarely radioactive isotopes, 22 Na, 24 Na, 36 Cl) 85,86 is administered (generally, one or more stable isotope) either orally or intravenously and allowed to equilibrate for about 3-4 h. During this time, the isotopes can exchange with hydrogen and oxygen in basal biochemical and metabolic reactions and diffuse the entire body in a matter similar to that observed in water.…”