The team, led by materials chemist Trisha L. Andrew, believe this could help unlock the development of wearable biosensors. As Andrew explains, "Batteries or other kinds of charge storage are still the limiting components for most portable, wearable, ingestible or flexible technologies. The devices tend to be some combination of too large, too heavy and not flexible."
The method uses a micro-supercapacitor and combines vapour-coated conductive threads with a polymer film, plus a special sewing technique to create a flexible mesh of aligned electrodes on a textile backing. The resulting solid-state device has a high ability to store charge for its size, and other characteristics that allow it to power wearable biosensors.
Andrew adds that while researchers have remarkably miniaturised many different electronic circuit components, until now the same could not be said for charge-storing devices. She claims that with this research, they have shown that they can “literally embroider a charge-storing pattern onto any garment using the vapour-coated threads that our lab makes. This opens the door for simply sewing circuits on self-powered smart garments."
Andrew points out that supercapacitors are ideal candidates for wearable charge storage circuits because they have inherently higher power densities compared to batteries.
But "incorporating electrochemically active materials with high electrical conductivities and rapid ion transport into textiles is challenging.” Andrew and colleagues show that their vapour-coating process creates porous conducting polymer films on densely-twisted yarns, which can be easily swelled with electrolyte ions and maintain high charge storage capacity per unit length as compared to prior work with dyed or extruded fibres.
Andrew notes that textile scientists have tended not to use vapour deposition because of technical difficulties and high costs, but more recently, research has shown that the technology can be scaled up and remain cost-effective.
She and her team are currently working to incorporate the new embroidered charge-storage arrays with e-textile sensors and low-power microprocessors to build smart garments that can monitor a person's gait and joint movements throughout a normal day.