High power density in a fully printed origami-inspired rolled thermoelectric generator enabled by paper self-folding

Thermoelectric generators (TEGs) can harvest waste heat for small electronics. However, printed planar TEGs are often limited by low thermocouple density within a given footprint. Here, we present a paper-based rolled thermoelectric generator (Rolled TEG) that autonomously transforms from a planar sheet into a cylindrical geometry via paper self-folding using a fully printed fabrication process. Silver nanoparticle ink is inkjet printed to form electrodes and interconnects, while PEDOT:PSS is screen printed to form p-type thermoelectric legs, enabling series-connected architectures on paper substrates. The self-folding transformation rearranges thermocouples onto the inner cylindrical surface, increasing thermocouple density per projected installation area while preserving leg length and electrical connectivity. By systematically examining printing conditions and electrode pattern design, we clarify how internal resistance and output characteristics are governed and demonstrate that the rolled geometry enhances footprint-normalized power generation by achieving a footprint-normalized power density of 18.9 nW cm^-2, which is 28.1 times higher than that of the Planar TEG. This work establishes autonomous paper self-folding as an effective design strategy for compact, fully printed thermoelectric devices.