A Skin‐Interfaced, Miniaturized Microfluidic Analysis and Delivery System for Colorimetric Measurements of Nutrients in Sweat and Supply of Vitamins Through the Skin

Abstract

Nutrients play critical roles in maintaining core physiological functions and in preventing diseases. Technologies for delivering these nutrients and for monitoring their concentrations can help to ensure proper nutritional balance. Eccrine sweat is a potentially attractive class of biofluid for monitoring purposes due to the ability to capture sweat easily and noninvasively from nearly any region of the body using skin‐integrated microfluidic technologies. Here, a miniaturized system of this type is presented that allows simple, rapid colorimetric assessments of the concentrations of multiple essential nutrients in sweat, simultaneously and without any supporting electronics – vitamin C, calcium, zinc, and iron. A transdermal patch integrated directly with the microfluidics supports passive, sustained delivery of these species to the body throughout a period of wear. Comparisons of measurement results to those from traditional lab analysis methods demonstrate the accuracy and reliability of this platform. On‐body tests with human subjects reveal correlations between the time dynamics of concentrations of these nutrients in sweat and those of the corresponding concentrations in blood. Studies conducted before and after consuming certain foods and beverages highlight practical capabilities in monitoring nutritional balance, with strong potential to serve as a basis for guiding personalized dietary choices.

A wearable electrochemical biosensor for the monitoring of metabolites and nutrients

“…Sweat is an important body fluid containing a wealth of chemicals reflective of nutritional and metabolic conditions [24][25][26][27] . The progression from blood analyses to wearable sweat analyses could provide great potential for non-invasive, continuous monitoring of physiological biomarkers critical to human health [28][29][30][31][32][33][34][35][36][37][38] . However, currently reported wearable electrochemical sensors focus primarily on a limited number of analytes including electrolytes, glucose and lactate, owing to the lack of a suitable continuous monitoring strategy beyond ion-selective and enzymatic electrodes or direct oxidation of electroactive molecules [25][26][27][34][35][36][37][38][39][40] .…”

Biocompatible Ionic Liquids in High-Performing Organic Electrochemical Transistors for Ion Detection and Electrophysiological Monitoring

“…Similarly, no significant change in the current was observed with interfering ion concentrations (100 mM Mg 2+ , 100 mM Ca 2+ , and 160 mM Na + ) cast on the K + selective OECT, as compared to the lowest K + physiological concentration (1 mM) in human sweat (Figure i). However, it is worth mentioning that Mg 2+ and Ca 2+ concentrations in human sweat are significantly lower than 100 mM (Ca 2+ and Mg 2+ ranges in human sweat are 0.2–11 mM and <2.5 mM, respectively). Therefore, both (Na + and K + ) ISM functionalized OECTs are highly selective for specific ion detection without much interference by Mg 2+ , Ca 2+ , K + , and Na + in the physiological condition.…”

A Comprehensive Review of the Recent Developments in Wearable Sweat-Sensing Devices

“…Reeder et al proposed an epidermal patch for colorimetric sensing integrated with microfluidic and water-proof electronic systems that can perform real-time physiological measurements on swimmers and dryland athletes [ 110 ]. In particular, most colorimetry sensing applies epidermal patches as wearable devices, as this device can be used for the single-shot measurement of sweat biomarkers once they change color, as reported by previous studies [ 111 , 112 ].…”

“…Colorimetric sensors [ 191 ] and fluorescent sensors [ 231 ] are the forms of optical sensing most found in recent SSDs. Kim et al reported a soft, thin colorimetric patch mounted with a microfluidic device that consists of passive valving [ 112 ]. Flowing sweat in their colorimetry sensing channel changed the color indicators depending on the loss of iron, zinc, calcium, and vitamin C nutrients.…”