A 3D-printed flexible microsupercapacitor with novel electrode architecture and plasma surface functionalization for miniaturized energy-storage applications

Three-dimensional (3D) microsupercapacitors (MSCs) are miniaturized energy-storage devices characterized by short charge–discharge cycles, high power densities, and low environmental impact. However, their low capacitance remains a critical limitation due to the poor conductivity and limited specific surface area (SSA) of conventional electrode materials. Here, we present a strategy combining 3D printing with advanced interdigitated electrode architectures and plasma surface functionalization to enhance electrochemical performance. Plasma treatment of carbon black (CB)-based 3D MSC electrodes using O₂ + CF₄ gases increased the SSA by 255 % and root-mean-square roughness by 310 %. The formation of surface C-O and C-F bonds enhanced electrolyte/ion adsorption, yielding an areal capacitance (Cₐ) of 6.73 mF/cm², significantly higher than that of pristine MSCs (2.11 mF/cm²) at 60 μA/cm². Incorporation of silver current collectors within advanced CB/Ag/CB 3D electrodes further improved Cₐ by ∼7-fold, achieving 48.6 mF/cm² and a volumetric capacitance of 5.45 F/cm³, with an energy density of 3.25 μWh/cm². The flexible 3D MSC module (3 series × 3 parallel 3D MSCs) demonstrated excellent mechanical and electrochemical stability, highlighting its potential for wearable electronics and miniaturized Internet-of-Things devices.