Researchers at Imperial College London have developed a low cost electrode that can be embedded in face masks and clothing as sensors to monitor breathing, heart rate and ammonia levels.
The electrodes could be used for monitoring exercise, sleep, and stress to diagnosing and monitoring disease through breath and vital signs.
The electrodes use a new cotton-based conductive thread called Pecotex that is compatible with industry-standard computerised embroidery machines. A metre of thread costing 15c can connect up to ten sensors.
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The Pecotex thread is built from poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS,) and is machine washable, less breakable and more electrically conductive than commercially available silver-based conductive threads. This allows more layers to be added to the materials to create more complex sensors. Following embroidery, Pecotex demonstrated lower electrical resistance than the silver-based threads and retained their conductivity after 15 washing cycles.
The researchers fabricated three different classes of proof-of-concept devices including a t-shirt with embroidered electrodes for measuring the electrical activity of the heart by electrocardiography (ECG) as well as a disposable mask containing embroidered electrodes for monitoring respiration electrically and embroidered gas sensors for sensing ammonia. The embroidered electrodes retained the intrinsic properties of the fabric such as wearability, breathability and feel-on-the-skin.
“The flexible medium of clothing means our sensors have a wide range of applications. They’re also relatively easy to produce which means we could scale up manufacturing and usher in a new generation of wearables in clothing,” said Fahad Alshabouna, a researcher at Imperial’s Department of Bioengineering.
The research team embroidered the sensors into a face mask to monitor breathing, a t-shirt to monitor heart activity, and textiles to monitor gases like ammonia, a component of the breath that can be used to track liver and kidney function. The ammonia sensors were developed to test whether gas sensors could also be manufactured using embroidery.
“We demonstrated applications in monitoring cardiac activity and breathing, and sensing gases. Future potential applications include diagnosing and monitoring disease and treatment, monitoring the body during exercise, sleep, and stress, and use in batteries, heaters, anti-static clothing,” said Fahad.
“Pecotex is high-performing, strong, and adaptable to different needs. It’s readily scalable, meaning we can produce large volumes inexpensively using both domestic and industrial computerised embroidery machines,” said Dr Firat Guder at the Department of Bioengineering
“Our research opens up exciting possibilities for wearable sensors in everyday clothing. By monitoring breathing, heart rate, and gases, they can already be seamlessly integrated, and might even be able to help diagnose and monitor treatments of disease in the future.”
Next, the researchers will explore new application areas like energy storage, energy harvesting and biochemical sensing, as well as finding partners for commercialisation.
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