Flexible, transparent, arrayable interdigitated electrode-based micro-supercapacitor with tunable voltage/current windows

Flexible transparent micro-supercapacitors (FTMSCs) have emerged as a key resource due to their high transmittance, durable mechanical flexibility, and excellent electrochemical performance. However, due to the limitations imposed by electrode materials and fabrication processes, the voltage window of most reported supercapacitors remains relatively low (typically below 1 V) and lacks tunability. Therefore, this study reveals an innovative method for preparing PPy/Au/Ag-wall FTMSCs using micro-3D printing combined with directional electrochemical polymerisation (ECP). By employing a high-resolution multilayer Ag-wall electrode structure and optimising the polymerisation process of polypyrrole (PPy) on the Ag-wall, the FTMSCs with a transmittance of approximately 80.07 %, an areal capacitance of 23.36 mF cm⁻², and an energy density of 3.24 μWh cm⁻² have been successfully fabricated. The results demonstrated excellent performance under various bending conditions, with a capacitance retention rate of 90.6 % after 1000 bending cycles. Additionally, the flexible adjustment of the voltage window was achieved through series and parallel connections of the Ag-wall within a limited area of 0.685 cm², enabling a voltage range from 1 V to 6 V and high output power. The fabricated FTMSC provides a promising foundation for the application in low-cost, large-scale wearable and high-performance electronic devices.