how sweat sensors could play a critical role in monitoring our health

sweat is a biological fluid — like blood, saliva and urine — that contains metabolites, electrolytes, proteins and hormones. the levels of these vary depending on a person’s health. wearable sweat sensors have been developed to  track users’ health condition and monitor the levels of these substances (known as analytes) in sweat .

lactate is considered an important biomarker thanks to its involvement in anaerobic metabolism. the undesired accumulation of lactate in muscles can result in fatigue, so changes in the concentration of lactate in sweat can be used to monitor fatigue. at simon fraser university’s additive manufacturing laboratory, we have developed  a flexible sensor for sweat lactate .

sweat challenges

one of the first hurdles in developing a reliable sweat sensor is the difficulty of collecting and routing of sweat. there are various methods for sampling sweat for sensing. one of the most representative approaches for collecting sweat is using  microfluidic systems with channels that deliver sweat .

absorbent materials like cloth can also be  used for sweat sampling for sensing . however, sampling sweat takes time, and how to handle the sweat sample and supply it in the sensing region in a continuous and stable manner remains a challenge for real-time measurement through continuous sensing of freshly generated sweat.

one of the most recent demonstrations used an  integrated microfluidic system with thermo-responsive hydrogels . this system demonstrated significant potential for programmable control of sweat routing and sensing, which will improve the sweat handling for future sweat sensors.

secondly, there is no single representative analyte in sweat.  sweat sensors can detect analytes  such as  ammonia, ethanol , ions, glucose, lactate, sweat chloride, ph, urea and creatinine, but there isn’t a single analyte that can independently provide a significant picture of an individual’s health. this means that sweat sensors must be able to measure many different substances in sweat to provide a useful report.

there are several sweat sensor products coming to market  that measure analytes like the protein cytokine  and  glucose and lactate .

we still need to determine the relationship between  levels of analyte in sweat and blood , and  the relationship between sweats from different parts of body . this recent study demonstrated that sweat bio-sensing can provide blood-correlated ethanol concentration data, which gives us hope that it may be possible to find blood-correlated concentrations for other analytes as well.

powerful solutions

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