Potential applications for this range from monitoring exercise, sleep quality and stress, to diagnosing and monitoring disease through breath and vital signs.
The sensors cost very little to manufacture, spun from a new Imperial-developed cotton-based conductive thread called Pecotex. For around 10p, one metre of thread can be produced to seamlessly integrate more than ten sensors into clothing. Pecotex is also compatible with industry-standard computerised embroidery machines.
Fahad Alshabouna, first author of the research and a PhD candidate at Imperial's Department of Bioengineering, said: "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."
The research team has embroidered the sensors into a face mask to monitor breathing, a t-shirt to monitor heart activity, and other textiles to monitor gases such as 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.
Fahad added: "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."
Wearable sensors, like those found on smartwatches such as the Apple Watch, enable the user to continuously and non-invasively monitor certain health signs and their general wellbeing. However, there is a lack of suitable conductive threads on the market, which explains why wearable sensors have not been widely integrated into clothing.
Imperial's Pecotex material is machine washable and is less breakable and more electrically conductive than commercially available silver-based conductive threads, meaning that more layers can be added to create more complex types of sensors.
The researchers tested their sensors against commercially available silver-based conductive threads both during and after they were embroidered into clothing. During embroidery, the tests suggested that Pecotex was more reliable and less likely to break, allowing for additional layers to be embroidered one on top of the other. Following embroidery, Pecotex also demonstrated lower electrical resistance than the silver-based threads, meaning they were better at conducting electricity.
Lead author Dr Firat Guder, also from Imperial's Department of Bioengineering, said: "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.
"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."
The researchers now plan to explore new application areas, such as energy storage, energy harvesting and biochemical sensing, as well as finding partners for commercialisation of the sensor thread.
The research article – 'PEDOT:PSS-Modified Cotton Conductive Thread for Mass Manufacturing of Textile-Based Electrical Wearable Sensors by Computerised Embroidery' – has been published in the journal Materials Today.
