Omnidirectional 3D Printing of PEDOT: PSS Aerogels with Tunable Electromechanical Performance: A Playground for...

The next generation of soft electronics will expand to the third dimension. This will require the integration of mechanically compliant 3D functional structures with stretchable materials. Here, omnidirectional direct ink writing (DIW) of poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) aerogels with tunable electrical and mechanical performance is demonstrated, which can be integrated with soft substrates. Several PEDOT:PSS hydrogels are formulated for DIW and freeze-dried directly on stretchable substrates to form integrated aerogels displaying high shape fidelity and minimal shrinkage. This technology demonstrates 3D-structured stretchable interconnects, planar thermoelectric generators for skin electronics, and vertically printed high aspect ratio thermoelectric pillars with ultralow thermal conductivity of 0.065 W m^-1 K^-1. The aerogel pillars outpower their dense counterparts in realistic energy harvesting scenarios, where contact resistances cannot be ignored and produced up to 26 nW cm^-2 (corresponding to a gravimetric power density of 0.76 mW kg^-1) for a difference of temperature of 15 K. Here, promising advancements in soft and energy-efficiency electronic systems relevant to soft robotics and wearables are suggested.