According to the paper, developing soft wearable electronics with a long-lasting source of energy remains a big challenge. Supercapacitors are seen as a potential solution, but most such devices are rigid. Those compressible supercapacitors developed so far have been made with carbon-coated polymer sponges, but the coating material tends to bunch up and compromise performance.
Guruswamy Kumaraswamy, Kothandam Krishnamoorthy and colleagues from India’s National Chemical Laboratory prepared polymer gels in green tea extract, a step which infuses the gel with polyphenols. The polyphenols converted a silver nitrate solution into a uniform coating of silver nanoparticles, after which thin layers of gold and poly were applied.
The resulting supercapacitor is said to have a power density of 2.715kW/kg and an energy density of 22Wh/kg. This, says the team, is enough to operate a heart rate monitor, LEDs or a Bluetooth module.