(a) Schematic illustration of the synthesis of PECOTEX and a photo of the thread on a bobbin. The inset shows the chemical structure of the product of the crosslinking reaction between PEDOT:PSS and cellulose surfaces of the cotton thread; (b) Process flow for computerized embroidery of PECOTEX on cotton fabric (interdigitated electrodes) and 1 mm thick silicone substrates.Researchers at Imperial College London and King Abdulaziz City for Science and Technology have produced a conductive cotton thread that can be machine-embroidered onto textiles to create wearable sensors [Alshabouna et al., Materials Today (2022), https://doi.org/10.1016/j.mattod.2022.07.015].
Wearable sensors offer the possibility of continuous, real time health monitoring – of heart rate, breathing, activity, or even glucose levels or ions in sweat – without the need for bulky or invasive devices strapped to the body. Such monitoring would open up a new paradigm in health monitoring, facilitating earlier diagnosis and improved assessment of treatment effectiveness. To date, however, most wearable sensors come in the form of watches, patches or straps. Going a step forward to incorporate monitoring devices directly into textiles or clothing would be highly attractive. But this requires that the materials used to fabricate sensing devices are compatible with textile manufacturing and usage, including repeated washing. So far, most conductive threads do not maintain their properties sufficiently well after manufacturing or incorporation into textiles.
To meet this complex set of requirements, Firat Güder of Imperial College London and his colleagues created a cotton thread modified with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) that is conductive and robust enough to withstand industrial computerized machine embroidery and machine washing. The thread, PECOTEX, is produced via a crosslinking reaction using divinyl sulfone (DVS), which binds PEDOT:PSS tightly to the cotton fibers of the thread. Commercially available cotton thread is simply drawn through a PEDOT:PSS-based conductive ink after pre-treatment to strip the fibers of fatty and waxy residues. The thread can be produced in large quantities via a roll-to-roll approach for as little as $0.15 per meter.
“[Our sensors are] relatively easy to produce, which means we could scale up manufacturing,” says first author of the work, Fahad Alshabouna.
As a demonstration of the possibilities, the researchers used the thread to embroider sensors on a T-shirt to measure heart activity, into a face mask to monitor breathing, and onto textiles to detect gases like ammonia.
“Future potential applications [could] include diagnosing and monitoring disease and treatment, monitoring the body during exercise, sleep, and stress, and use in batteries, heaters, anti-static clothing,” adds Alshabouna.
The approach using DVS as a crosslinker could also be expanded to attach other useful functional elements to cotton fibers.
“PECOTEX is high-performing, strong, and adaptable to different needs,” says Güder. “Our research opens up exciting possibilities for wearable sensors in everyday clothing.”