3D Printing of Nanomaterial-Based Bioelectronics with a Metamaterial-Inspired Near-Field Electromagnetic Structure

3D printing of nanomaterials can enable the creation of freeform architectures and multifunctional devices with unprecedented versatility. The full potential of this technology, however, has so far been limited by the inability to selectively anneal the printed nanomaterials, a critical step to enhance performance. Here, we demonstrate the ability to selectively and locally anneal 3D printed nanomaterials <i>in situ </i>on a broad range of temperature-sensitive substrates by focusing near-field electromagnetic waves using a metamaterial-inspired near-field electromagnetic structure (Meta-NFS). The near-field microwave 3D printing (NFP) enables exceptional control of printed nanomaterial annealing parameters, allowing the creation of spatially freeform microstructure where the electronic and mechanical properties can be locally programmed. NFP significantly broadens the possible class of materials compatible with an additive manufacturing process, enabling the creation of hybrid multi-functional constructs and printing of functional electronics even on temperature-sensitive substrates.