Enhanced Wire-Shaped Micro-Supercapacitor Treated with a Continuous Surface Atmospheric Pressure Plasma Jet Approach

Microscale, wire-shaped flexible supercapacitors are gaining significant attention due to the growing demand for wearable electronics and microrobotic technologies. Among various materials, copper sulfide stands out as an ideal candidate because of its superior electrochemical properties, which can be attributed to its nanostructured composition. This structure enhances the surface area, reduces ion transport distances, and improves charge-discharge kinetics. However, conventional electrode synthesis methods-such as annealing and hydrothermal processes-are limited by long production times and scalability issues, making them unsuitable for wire-shaped supercapacitor development. In this study, an innovative fabrication technique using an atmospheric pressure plasma jet (APPJ) for both surface treatment and material synthesis is proposed. By integrating the APPJ with a winding mechanism, roll-to-roll processing for continuous production is enabled, significantly enhancing the scalability of the manufacturing process. The fabricated wire-shaped microscale electrodes demonstrate high specific capacitance (153.39 mF cm^-2), specific energy density (15.48 µWh cm^-2), and excellent capacitance retention (91.32%) after 30 000 charge-discharge cycles. Furthermore, a wire-shaped solid-state flexible asymmetric supercapacitor is assembled using the fabricated electrodes in a coaxial configuration. The supercapacitor exhibits exceptional flexibility and energy storage performance, underscoring the practical applicability of the proposed method for advanced electronics.