Scalable Semi-Automatic Screen-Printing of Redox-Enhanced PANI–Carbon Inks for Flexible Micro-Supercapacitors

Abstract With the development of wearable electronics, Internet of Things devices, and integrated sensor systems, flexible and miniaturized energy-storage technologies are increasingly sought. In the present work, we present a scalable approach to manufacture flexible micro-supercapacitors (MSCs) using a commercial carbon ink doped with 5 wt % polyaniline (PANI) through semi-automatic screen printing on polyethylene terephthalate (PET) substrates. Rheological tests show that the PANI–carbon ink is highly shear-thinning, highlighting that the presence of PANI maintains the flow properties needed for the screen-printing process and also allows well-defined interdigitated electrode structures to be achieved. The hybrid electrode exhibits a maximum areal capacitance of 11.68 mF cm–2 and an areal energy density of 0.584 µWh cm–2. The power-law and Dunn analysis results support mixed surface and diffusion charge storage with a greater capacitive component at higher scan rates. After 15,000 GCD cycles, the capacitance retained by the MSC is about 94% with a calculated coulombic efficiency of 98.24% at the 15,000th cycle. The flexibility is shown by maintaining 98.2% capacitance retention under bending. Moreover, series connections of MSCs increase the operating voltage to 0.6–1.2 V, parallel connections boost the charge-storage capacity and the integrated devices can drive a red LED. These findings illustrate a scalable way to make redox-active polymers a part of commercial screen-printing inks for mechanically flexible, practically integrated microscale energy-storage devices.