Wearable microfluidic patch with integrated capillary valves and pumps for sweat management and multiple biomarker analysis

Abstract

Wearable sweat sensors are essential for providing insight into human physiological health. The currently developed microfluidic sweat sensors have demonstrated the function of collecting and storing sweat. However, they detect more average concentrations of substances based on time periods, which leads to the fact that in situ real-time measurement for multiple biomarkers remains a grand challenge. Here, we propose a wearable epidermal microfluidic patch with integrated microfluidic pumps and micro-valves for accelerated and continuous collection of the sweat, where the micro-pumps ensure the complete separation of old and new sweat for real-time detection of real concentration of biomarkers in sweat. The biomarker concentration at different time periods is detected by introducing a burst valve, which is used to assist in the analysis of the real-time detection. A quantitative relationship between the minimum burst pressure difference required for sequential collection and the size of the microchannel structure is established to overcome the effects of additional resistance at the gas–liquid interface. Additionally, the sensing modules, including sodium ion, chlorine ion, glucose, and pH level in sweat, are integrated into the patch to realize in situ, real-time detection of multiple biomarkers in the human sweat, decoding the correlation between changes in substance concentrations and physiological conditions. This work provides a unique and simplifying strategy for developing wearable sweat sensors for potential applications in health monitoring and disease diagnostics.

Epidermal Wearable Biosensors for Monitoring Biomarkers of Chronic Disease in Sweat

“…[ 17 , 18 ]. Therefore, due to the high-density distribution of eccrine sweat glands both in children and adults and the considerable sweat secretion, sweat can be collected non-invasively using a compact epidermal wearable biosensor [ 19 , 20 , 21 ].…”

“…Now, studies have confirmed that perspiration is mainly composed of water (99%); metabolites (such as lactate, glucose, urea, cortisol, hydroxybutyrate, etc.) [ 20 , 25 , 26 , 27 , 28 ]; electrolytes (such as Na + , K + , Cl − , etc.) [ 20 , 29 , 30 ]; trace elements (such as Zn 2+ and Cu 2+ , Fe 3+ , etc.)…”

“…[ 20 , 25 , 26 , 27 , 28 ]; electrolytes (such as Na + , K + , Cl − , etc.) [ 20 , 29 , 30 ]; trace elements (such as Zn 2+ and Cu 2+ , Fe 3+ , etc.) [ 31 , 32 , 33 ]; a small amount of macromolecules (such as cytokines IL-31, IL-6, TNF-α, IFN-γ, neuropeptide Y, etc.)…”

“…They are limited to certain conditions, such as strenuous exercise, as shown in Table 2 . Usually, these biosensors are made of paper or elastic silicone and put on the skin of the arm or forehead through transparent medical tape or double-sided tape ( Figure 2 ) [ 20 , 84 , 85 , 86 , 87 , 88 ], since the arm and forehead normally perspire faster than the rest of the body surface. Also, they can be integrated into an arm guard, wristband, or headband ( Figure 2 ) [ 22 , 84 , 89 ].…”

“…The detected sweat biomarkers are usually closely related to exercise functions, including glucose, lactate, cortisol, Na + , Cl −1 , K + , etc. [ 20 , 22 , 84 , 85 , 86 , 87 , 88 , 89 , 90 ]. Although studies have proven the feasibility of detecting biomarkers in human sweat under special conditions (strenuous exercise), the sweat secretion rate fluctuates greatly, which affects the accuracy and reliability of the results.…”