Researchers at The University of Western Australia have revealed that 3D-printing can be used to create a resonant microwave cavity via an aluminium-silicon alloy that shows superconductivity when cooled below the critical temperature of aluminium.

Professor Michael Tobar, an Australian Research Council Laureate Fellow from UWA’s School of Physics, said superconducting cavities were highly useful in many areas of physics, from quantum physics to particle accelerators.

Two groups at UWA, one led by Professor Tim Sercombe, an expert in materials and 3D printing, and the other led by Professor Michael Tobar, an expert in engineered quantum systems and novel cavity designs, combined their expertise to explore the superconducting properties of 3D-printed parts. The research was published today in Applied Physics Lettters, from AIP Publishing.

Professor Tobar said conductivity measured how easily an electrical current flowed through a material while superconductivity was this measure taken to its extreme.

3D printing is revolutionising many areas of manufacturing and science and particularly 3D printing of metals is being used in fields as diverse as customised medical implants, jet engine bearings and rapid prototyping for the automotive industry.

While many techniques can be used for 3D printing metals, most rely on computer-controlled melting or sintering (a high temperature process for fusing powder together) of a metal alloy powder by a laser or electron beam.

Professor Tobar said the mechanical properties of parts produced by this method had been well studied, but not enough attention had focused on their electrical properties.

“The physics of superconductivity is well understood, and it has been known for decades that aluminium exhibits superconductivity,” Professor Tobar said.

“But the 3D printing process relies on aluminium that’s far from pure and it undergoes several processes, such as atomisation, laser melting, furnace annealing etc. So we wanted to explore whether a range of known superconducting metals could successfully be 3D printed and retain their desirable electrical property.”

Beyond measuring the superconductivity, the researchers wanted to show that they could do something potentially useful with this technique so they decided to 3D print a resonant microwave cavity.

“Using a device called a ‘vector network analyser,’ we excited electromagnetic modes of resonance at microwave frequencies inside the cavity and measured its quality factor, known as ‘Q’,” Professor Tobar said. “This is a measure of how long injected microwaves are stored within the cavity before being lost. It’s directly related to the surface resistance of the cavity walls.”

Through measurements of the Q-factor, the researchers were able to indirectly determine this resistance and show that the material becomes superconducting at 1.2 Kelvin.

“This result was surprising, given the very large concentration of non-superconducting silicon within the alloy,” he said. “It may open new possibilities for printing novel cavity configurations that are otherwise currently impossible for machine use.”

The team’s results are immediately useful as people can now craft a variety of components based on their work.