Direct ink writing of PEDOT:PSS inks for flexible micro-supercapacitors

Here, we fabricate poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)-based flexible micro-supercapacitors (MCSs) using direct ink writing (DIW) printing. To produce inks suitable for DIW printing, inks with various PEDOT:PSS concentrations are prepared, and their rheological properties and printability are systematically investigated. The optimized PEDOT:PSS ink allows stable printing without spreading and nozzle clogging issues, leading to the successful fabrication of well-defined interdigitated electrode patterns. The resulting PEDOT:PSS-based MSC exhibits high energy storage performance (2005 μF/cm² at 10 μA/cm²) and outstanding cycle stability (capacitance retention of 87% after 10,000 cycles). Taking advantage of the flexibility of the PEDOT:PSS electrode, the MSC maintains its performance even under bending stress. Moreover, the practicality of the system is demonstrated by tailoring the overall operating voltage and output capacitance through printing MSCs connected in series and parallel.