Rice University researchers have developed a 3D-printing process that uses focused microwaves to heat electronic ink during fabrication without damaging surrounding materials, solving a problem that’s blocked the field for more than a decade. The work, published April 13 in Science Advances, could enable a new class of hybrid electronic devices that weren’t previously possible to build.
The core obstacle has always been thermal processing. Printing functional electronics requires heating the ink to activate it, but that heat destroys the temperature-sensitive materials underneath. Yong Lin Kong, assistant professor of mechanical engineering at Rice’s George R. Brown School of Engineering and Computing, and longtime collaborator John Ho, an associate professor at the National University of Singapore and expert in microwave engineering, designed a solution they call Meta-NFS, short for metamaterial-inspired near-field electromagnetic structure. It concentrates microwave energy into a heating zone as small as 150 micrometers, roughly the diameter of a human hair.
“The ability to selectively heat the printed materials enables us to spatially program the ink’s functional properties, even when surrounded by temperature-sensitive material,” Kong said. “This allows us to integrate freeform electronics onto a broad range of substrates, including biopolymers and living biological tissue, all within a desktop-size printer without the needs of complex facilities or labor-intensive manual processes.”
By adjusting microwave parameters mid-print, the team can precisely control the microstructure of printed particles to create multifunctional circuitry with orders-of-magnitude differences in mechanical and electronic properties, all within a single printing process and without switching materials. The approach works across metals, ceramics, and thermoset polymers, and the microwaves can penetrate deeply enough to heat fully encapsulated materials.
The team’s proof-of-concept demonstrations pushed into biological territory. They printed wireless strain sensors onto ultrahigh-molecular-weight polyethylene, a biopolymer used in joint replacements, creating implants that could monitor stress or wear. They also printed wireless sensors directly onto a bovine femur bone and onto a living leaf.
Kong’s group is now using Meta-NFS as the foundation for ingestible electronic systems for personalized diagnostics, bionic devices that interface with biological organs, and 3D-printed soft robots and drones with integrated electronics. The research was funded by the Office of Naval Research and the National Institutes of Health.
Source: news.rice.edu
