Superconducting nanomaterial is flexible as cling film
Experimental physicists at Saarland University, Germany, have developed a thin nanomaterial with superconducting properties.
Below around -200°C, the materials conduct electricity without loss, levitate magnets and can screen magnetic fields. The particularly interesting aspect of this work is that the research team has succeeded in creating superconducting nanowires that can be woven into a flexible, ultra-thin film, making novel coatings for applications ranging from aerospace to medical technology possible.
The work is a collaborative effort involving the team led by Professor Uwe Hartmann at Saarland University and Professor Volker Presser of the Leibniz Institute for New Materials (INM), who also holds the Chair of Energy Materials at Saarland University. Their results have been published in a number of scientific journals.
Looking like nothing more than a charred black piece of paper, the superconductor material is essentially a woven fabric of plastic fibres and high-temperature superconducting nanowires. The electrons in the material can flow unrestricted through the cold immobilised atomic lattice. In the absence of electrical resistance, if a magnet is brought up close to a cold superconductor, the magnet effectively ‘sees’ a mirror image of itself in the superconducting material. So, 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.
Many superconducting materials available today are rigid, brittle and dense, which makes them heavy. The Saarland physicists have now succeeded in packing superconducting properties into a thin flexible film. ‘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,’ Prof Hartmann explained.
The low weight of the film is particularly advantageous. ‘With a density of only 0.05 grams per cubic centimetre, 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.
The experimental physicists made used electrospinning, which is usually used in the manufacture of polymeric fibres, to weave the material. ‘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 nanometres 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,’ explained Dr Michael Koblischka, one of the scientists in Hartmann‘s group.