Flexible Thread-Based Sweat Sensors Could Let Your Clothing Track Your Health, Fitness Levels

Based on conductive threads, the low-cost and lightweight sensors could be used in next-generation healthcare monitoring clothing.

Researchers from Tufts University, the Indian Institute of Technology (IIT), and the Center for Applied Brain and Cognitive Sciences have designed thread-based wearable healthcare sensors based on sweat analysis — and say the can be easily integrated into clothing.

The idea behind analyzing sweat using a wearable sensor isn't new: Caltech has developed a low-cost sensor designed to track stress, a multi-university team created a sensor for exercise monitoring which automatically heals when cut, and sweat sensors originally developed to market soft drinks have been repurposed to assist in the fight against COVID-19.

"Sweat is a useful fluid for heath monitoring since it is easily accessible and can be collected non-invasively," explains Trupti Terse-Thakoor, formerly a post-doctoral scholar at Tufts University School of Engineering and first author of the study. "The markers we can pick up in sweat also correlate well with blood plasma levels which makes it an excellent surrogate diagnostic fluid."

Terse-Thakoor and colleagues' creation is a flexible sensing patch which can be sewn directly into clothing to monitor general health or acute and chronic conditions by measuring biomarkers including electrolytes, metabolytes, and acidity in the wearer's sweat. The sensors themselves are made from conductive thread, coated so as to respond to the particular biomarker under observation. These sensors are then connected to wireless readout hardware, based on the Nordic Semiconductor nRF52832-powered RedBear BLE Module MB-N2.

In testing, the patches proved capable of measuring on a 5-30 second interval during physical exercise on a stationary bike — though, the paper notes, the data retrieved wasn't used to find any correlation between measured biomarkers and exertion levels.

"The sensor patch that we developed is part of a larger strategy to make completely flexible thread-based electronic devices," adds Professor Sameer Sonkusale, corresponding author. "Flexible devices woven into fabric and acting directly on the skin means that we can track health and performance not only non-invasively, but completely unobtrusively - the wearer may not even feel it or notice it."

The team's work has been published under open-access terms in the journal Flexible Electronics.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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