Highly stretchable CNT Fiber/PAAm hydrogel composite simultaneously serving as strain sensor and supercapacitor

The integration of different functional components into one device is attracting increasing attention. In this work, a high strength carbon nanotube (CNT) fiber/polyacrylamide (PAAm) hydrogel composite is developed by embedding quasi-sinusoidal shaped CNT fibers in PAAm hydrogel. Combination of ionic conductive hydrogel and wavy CNT fibers yields a highly stretchable and wearable device with integration of strain sensing component and electrochemical energy storage component. On the one hand, the CNT fiber/PAAm hydrogel (CFPH) composite shows an excellent strain sensing performance with a stretch-ability up to 100% in a wide frequency of 0.1–10 Hz. As a result, it is effective as stretchable and wearable strain sensor to monitor a range of small to large scale human activities. On the other hand, with two parallel quasi-sinusoidal shaped CNT fibers as electrodes and one ionic conductive PAAm hydrogel as electrolyte and separator simultaneously, the CFPH composite serves as a stretchable all-solid-state supercapacitor with an areal capacitance of 10.6 mF cm−2. The electrochemical performance of the CFPH composite under both static and dynamic loading is very stable, exhibiting a capacitance retention of 90.0% after 3000 charge-discharge cycles with dynamic stretching applied simultaneously. The developed dual-mode CNT fiber/PAAm hydrogel composite is promising to serve as two functional components in one device.