Sulfur-Functionalized Carbon Nanotubes with Inlaid Nanographene for 3D-Printing Micro-Supercapacitors and a Flexible Self-Powered Sensing System

Digital fabrication of miniaturized micro-supercapacitors (MSCs) holds immense promise for advancing customized, integrated microelectronic systems. As potential electrode materials, carbonaceous nanomaterials, such as carbon nanotubes (CNTs), stand out due to their excellent conductivity and mechanical robustness yet suffer from low ionic storage sites, which restrict further applications. Herein, we introduce a sulfur-assisted in situ activating strategy for obtaining sulfur-functionalized carbon nanotube frameworks integrated with inlaid graphene nanosheets (S-CNT/GNS). Specifically, sulfur functionality enriches the surface charge density with improved interfacial hydrophilicity, while the inlaid nanographene sheets provide abundant ionic adsorption sites. By direct 3D printing of the S-CNT/GNS ink, planar MSCs were fabricated with desirable functionality and outstanding electrochemical performance. Notably, the developed MSCs exhibit a high areal capacitance of 0.47 F cm^-2, an exceptional energy density of 64.6 μWh cm^-2, and a high-power density of 34.2 mW cm^-2. Furthermore, an all-flexible self-powered sensing system with photovoltaic cells and a stretchable sensor was built upon the customized S-CNT/GNS MSCs, demonstrating a highly effective capability for real-time monitoring of human physiological signals and body movements. This work not only presents a promising approach for the development of high-performance MSCs but also lays the groundwork for the creation of advanced wearable/flexible microelectronics systems.