@article{saha_fang_yokus_mukherjee_bozkurt_daniele_dickey_velev_2021, title={A Wearable Patch for Prolonged Sweat Lactate Harvesting and Sensing}, ISSN={["1558-4615"]}, DOI={10.1109/EMBC46164.2021.9630881}, abstractNote={Operating at low sweat rates, such as those experienced by humans at rest, is still an unmet need for state-of-the-art wearable sweat harvesting and testing devices for lactate. Here, we report the on-skin performance of a non-invasive wearable sweat sampling patch that can harvest sweat at rest, during exercise, and post-exercise. The patch simultaneously uses osmosis and evaporation for long-term (several hours) sampling of sweat. Osmotic sweat withdrawal is achieved by skin-interfacing a hydrogel containing a concentrated solute. The gel interfaces with a paper strip that transports the fluid via wicking and evaporation. Proof of concept results show that the patch was able to sample sweat during resting and post-exercise conditions, where the lactate concentration was successfully quantified. The patch detected the increase in sweat lactate levels during medium level exercise. Blood lactate remained invariant with exercise as expected. We also developed a continuous sensing version of the patch by including enzymatic electrochemical sensors. Such a battery-free, passive, wearable sweat sampling patch can potentially provide useful information about the human metabolic activity.}, journal={2021 43RD ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE & BIOLOGY SOCIETY (EMBC)}, author={Saha, Tamoghna and Fang, Jennifer and Yokus, Murat A. and Mukherjee, Sneha and Bozkurt, Alper and Daniele, Michael A. and Dickey, Michael D. and Velev, Orlin D.}, year={2021}, pages={6863–6866} }
 @article{saha_fang_mukherjee_knisely_dickey_velev_2021, title={Osmotically Enabled Wearable Patch for Sweat Harvesting and Lactate Quantification}, volume={12}, ISSN={["2072-666X"]}, url={https://doi.org/10.3390/mi12121513}, DOI={10.3390/mi12121513}, abstractNote={Lactate is an essential biomarker for determining the health of the muscles and oxidative stress levels in the human body. However, most of the currently available sweat lactate monitoring devices require external power, cannot measure lactate under low sweat rates (such as in humans at rest), and do not provide adequate information about the relationship between sweat and blood lactate levels. Here, we discuss the on-skin operation of our recently developed wearable sweat sampling patch. The patch combines osmosis (using hydrogel discs) and capillary action (using paper microfluidic channel) for long-term sweat withdrawal and management. When subjects are at rest, the hydrogel disc can withdraw fluid from the skin via osmosis and deliver it to the paper. The lactate amount in the fluid is determined using a colorimetric assay. During active sweating (e.g., exercise), the paper can harvest sweat even in the absence of the hydrogel patch. The captured fluid contains lactate, which we quantify using a colorimetric assay. The measurements show the that the total number of moles of lactate in sweat is correlated to sweat rate. Lactate concentrations in sweat and blood correlate well only during high-intensity exercise. Hence, sweat appears to be a suitable biofluid for lactate quantification. Overall, this wearable patch holds the potential of providing a comprehensive analysis of sweat lactate trends in the human body.}, number={12}, journal={MICROMACHINES}, author={Saha, Tamoghna and Fang, Jennifer and Mukherjee, Sneha and Knisely, Charles T. and Dickey, Michael D. and Velev, Orlin D.}, year={2021}, month={Dec} }
 @article{saha_fang_mukherjee_dickey_velev_2021, title={Wearable Osmotic-Capillary Patch for Prolonged Sweat Harvesting and Sensing}, volume={13}, ISSN={["1944-8252"]}, url={https://doi.org/10.1021/acsami.0c22730}, DOI={10.1021/acsami.0c22730}, abstractNote={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.}, number={7}, journal={ACS APPLIED MATERIALS & INTERFACES}, publisher={American Chemical Society (ACS)}, author={Saha, Tamoghna and Fang, Jennifer and Mukherjee, Sneha and Dickey, Michael D. and Velev, Orlin D.}, year={2021}, month={Feb}, pages={8071–8081} }