A Transfer Method for Embedding Conductive Fillers on the Surface of Multi-Scale Structures for 3D Flexible Conductors

This paper demonstrates a transfer method for embedding conductive fillers (e.g., metal nanowires (MWs) and multi-walled carbon nanotubes (MWCNTs)) on the surface of polymers (e.g., polydimethylsiloxane (PDMS), polyurethane (PU)) with various multi-scale structures to fabricate 3D flexible conductors. Conductive fillers were embedded on the surfaces of macro- and microstructures considering the optimal surface energy conditions for transferring spray-coated conductive fillers from 3D molds to the polymer networks. This transfer method achieves highly conductive and robust 3D flexible conductors without changing the mechanical properties (e.g., elastic modulus, ductility, and brittleness), generating cracks in the conductive layer, or losing the conductive fillers under repeated pressure. Consequently, the developed conductors applied to pressure sensors exhibited sensing stability by maintaining a constant initial value.