Wearable Osmotic-Capillary Patch for Prolonged Sweat Harvesting and Sensing

Abstract

Biomarkers in sweat are a largely untapped source of health information. Most of the currently available sweat harvesting and testing devices are incapable of operating under low-sweat rates such as those experienced by humans at rest. Here we analyze the in vitro and in vivo sampling of sweat through osmosis via the use of a hydrogel interfaced with the skin, without need for active perspiration. The hydrogel also interfaces with paper-based microfluidics to transport the fluid via capillary forces toward a testing zone and then evaporation pad. We show that the hydrogel solute content and area of the evaporation pad regulate the long-term extraction of sweat and its associated biomarkers. The results indicate that the platform can sample biomarkers from a model skin system continuously for approximately 12 h. On-skin testing of the platform on both resting and exercising human subjects confirms that it can sample sweat lactate directly from the surface of skin. The results highlight that lactate in sweat increases with exercise and as a direct result of muscle activity. Implementation of such new principles for sweat fluid harvesting and management via wearable patch devices can contribute toward the advancement of next generation wearables.

Modulus and adhesion of Sylgard 184, Solaris, and Ecoflex 00‐30 silicone elastomers with varied mixing ratios

“…Additionally, these elastomer systems can be enhanced through the addition of non‐covalent bonds to enhance toughness and dissipate energy 39–41 . Although many silicones are available on the market, a few of the most widely implemented are Sylgard 184, 4,5,32,42,43 Solaris, 30,44 and Ecoflex 00–30 4,16,45 . Their widespread use has led to studies on their mechanical properties as a function of variables like strain rate, processing conditions, manufacturer, and mixing ratio of the two parts 1,4,5,32,34,38,46,47 .…”

State of Sweat: Emerging Wearable Systems for Real-Time, Noninvasive Sweat Sensing and Analytics

“…Adapted with permission from ref , Copyright 2019 American Association for the Advancement of Science, and ref , Copyright 2018 John Wiley and Sons, respectively. Alternative approaches seek to collect sweat passively using (C) thermal stimulation via showering or (D) wicking materials . Adapted with permission from ref , Copyright 2019 The Royal Society of Chemistry, and ref , Copyright 2021 American Chemical Society, respectively.…”

“…Alternative approaches seek to collect sweat passively using (C) thermal stimulation via showering or (D) wicking materials . Adapted with permission from ref , Copyright 2019 The Royal Society of Chemistry, and ref , Copyright 2021 American Chemical Society, respectively.…”

Skin Patchable Sensor Surveillance for Continuous Glucose Monitoring

“…105,106 The stratum corneum (epidermis) is the outermost layer of the skin, which forms the major diffusion barrier for almost all the environmental compounds. 107,108 It is challenging to obtain information on such glucose concentrations from the epidermis, where it is even more challenging to choose a compatible material with feasible mechanistic designs that can support the electronics and build into a single ultrathin platform. Second, the human tissue is soft, anisotropic, heterogeneous, viscoelastic, curvilinear that can undergo regular multi-axes deformations.…”