All-printed, interdigitated, freestanding serpentine interconnects based flexible solid state supercapacitor for self powered wearable electronics

摘要

While the textile based stretchable supercapacitors have been demonstrated as efficient charge storage devices, challenges in developing self powered wearable devices still exist. The present work describes a screen printed flexible and stretchable supercapacitor that can act as an energy buffering element for powering wearable fitness monitoring devices. The supercapacitor possesses interdigitated shaped intrinsically stretchable electrodes with free-standing serpentine interconnects. The symmetric supercapacitor relies on carbon nanotube and poly(aniline) as active materials and polyurethane as a stretch enduring binder. Such in-plane supercapacitors are realized by initially printing on a paper substrate, pre-coated with a water soluble layer, and then transferred onto a pre-strained elastomeric substrate. The supercapacitor showed excellent mechanical resiliency even though subjected to intense mechanical deformations. The electrode possessed highest areal capacitance of 167 mF/cm(2) at a current density of 0.4 mA/cm(2) and showed appreciable areal energy and power density of 14.9 mu Wh/cm(2) and 0.29 mW/cm(2), respectively. The supercapacitor showed conformal integration with the stretchable sweat band and which (3 devices, in series) can independently power a red light emitting diode. In combination with a flexible solar cell and a custom-made low power booster, the supercapacitor can continuously powers the wearable pulse rate sensor even in the presence of poor sunlight intensity.