A team of experimental physicists at Saarland University have developed something that seems pretty unremarkable at first sight. It looks like nothing more than a charred black piece of paper. But appearances can be deceiving. This unassuming object is a superconductor. If a superconductor and a magnet are placed in close proximity to one another and cooled with liquid nitrogen they will repel each another and the magnet levitates above the superconductor. It’s a bit like a low-temperature version of the hoverboard from the ‘Back to the Future’ films.
Many of the common superconducting materials available today are rigid, brittle and dense, which makes them heavy. The Saarbrücken physicists have now succeeded in packing superconducting properties into a thin flexible film. The material is a essentially a woven fabric of plastic fibres and high-temperature superconducting nanowires. “That makes the material very pliable and adaptable – like cling film. Theoretically, the material can be made to any size. And we need fewer resources than are typically required to make superconducting ceramics, so our superconducting mesh is also cheaper to fabricate,” explains Uwe Hartmann, Professor of Nanostructure Research and Nanotechnology at Saarland University.
The low weight of the film is particularly advantageous. “With a density of only 0.05 g/m³, the material is very light, weighing about a hundred times less than a conventional superconductor. This makes the material very promising for all those applications where weight is an issue, such as in space technology. There are also potential applications in medical technology,” explains Hartmann. The material could be used as a novel coating to provide low-temperature screening from electromagnetic fields, or it could be used in flexible cables or to facilitate friction-free motion.
In order to be able to weave this new material, the experimental physicists made use of a technique known as electrospinning, which is usually used in the manufacture of polymeric fibres. “We force a liquid material through a very fine nozzle known as a spinneret to which a high electrical voltage has been applied. This produces nanowire filaments that are a thousand times thinner than the diameter of a human hair, typically about 300 nm or less. We then heat the mesh of fibres so that superconductors of the right composition are created. The superconducting material itself is typically an yttrium-barium-copper-oxide or similar compound,’ explains Dr. Michael Koblischka, one of the research scientists.
Now the research team is looking for commercial and industrial partners with whom they can develop their system for practical applications.