Near-Field Electromagnetic 3D Printing for Nanomaterials-Based Electronics

The inability to selectively anneal printed materials on a broad range of temperature-sensitive constructs has limited the potential functional complexity and performance of 3D printed electronics. Thermal annealing of 3D printed nanomaterials is a critical process that dictates electronic performance by (1) merging otherwise disconnected nanomaterials, (2) reducing defects and interfaces, (3) removing polymeric additives, and (4) improving contact between printed layers. Prior works primarily rely on heating the entire printed object post-printing in a bulk annealing process, which severely limits the possible multimaterial integration and geometrical configurations. Here, we demonstrate the ability selectively and locally anneal 3D printed nanomaterials <i>in situ </i>on a broad range of temperature-sensitive substrates, including plant media and low-melting-temperature polymers, by exploiting metamaterial-inspired electromagnetic structures. The demonstrated near-field electromagnetic 3D printing (NFP) enables exceptional control of printed nanomaterial annealing parameters, creating spatially freeform microstructure where the electronic and mechanical properties can be locally programmed in a multimaterial construct. We envision that NFP significantly broadens the possible class of materials compatible with additive manufacturing processes, enabling the creation of hybrid multi-functional constructs and the integration of functional electronics on temperature-sensitive constructs.