Three-dimensional printing of nanomaterials-based electronics with a metamaterial-inspired near-field electromagnetic structure.

Three-dimensional (3D) printing can create freeform architectures and electronics with unprecedented versatility. However, the full potential of electronic 3D printing has so far been limited by the inability to selectively anneal the printed materials, especially on temperature-sensitive substrates. Here, we achieve highly selective and rapid volumetric heating of 3D-printed nanomaterials and polymers in situ by focusing microwaves using a metamaterial-inspired near-field electromagnetic structure (Meta-NFS). In contrast to previous work, the Meta-NFS achieves the spatial resolution and power density needed to 3D print freeform microstructures where the electronic and mechanical properties can be locally programmed even within optically opaque materials. By broadening the material palettes compatible with 3D printing, near-field microwave 3D printing with Meta-NFS enables classes of electronics that are otherwise challenging to create.