In a recently published paper, a team led by Rice University’s Yong Lin Kong has explained a new 3D-printing process with focused microwaves that overcomes a fundamental constraint of electronics 3D printing that has limited the field’s potential for more than a decade: the inability to heat printed ink (a crucial processing step) without damaging the materials underneath.
Above: The printing of freestanding silver microarchitecture with a 30-μm trace diameter on a leaf, demonstrating the ability to print on a temperature-sensitive substrate
The ability to integrate functional materials and spatially program their properties governs both device performance and the limits of what can be built. Existing manufacturing approaches are fundamentally limited in both aspects. Electronic components, for instance, are fabricated in massive, centralised foundries, often decoupled from the final device. Integrating them requires complex, labor-intensive assembly that constrains both the form and the function of what can ultimately be created.
Multimaterial 3D printing should, in principle, allow fabrication of free-form architectures in which electronic and mechanical properties are programmed directly into the structure. However, the thermal processing required to render printed electronic inks functional destroys the very materials these devices require.
Kong’s team demonstrates that by concentrating microwave energy into a confined heating zone as small as the diameter of a human hair, the researchers can selectively heat the electronic ink during the 3D-printing process while keeping the surrounding material relatively cool and thereby reducing potential damage.
“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,” said Kong, assistant professor of mechanical engineering at Rice’s George R. Brown School of Engineering and Computing. “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.”