Medical magnets

Technologies that use magnets could be made smaller and at lower cost thanks to superconducting magnets developed in Cambridge.

The innovation from Magnifye, a Cambridge University spin-out, would increase the power density of magnets used to produce energy in electric motors.

The magnets, which are 10 times stronger than conventional magnets, are so powerful that a 1in sample could potentially support the weight of a seven-tonne truck.

Tim Coombs, the Cambridge engineering lecturer who is behind Magnifye, said the magnets are created by magnetising a superconductor with a specially developed heat engine.

The engine creates a magnetic field by heating the edge of a ferromagnetic material. As the heat travels through this material, Coombs explained, it changes its permeability and creates a magnetic wave. A superconductor exposed to this wave would become magnetised.

The company has received Proof of Concept funding from the East of England Development Agency (EEDA) to explore companies interested in developing machines using the magnets.

The potential of the technology is already attracting interest from one of the world's largest engine makers, which is reportedly piloting Magnifye's technology for use in marine applications.

In the renewable energy sector, Magnifye has been working with Siemens to potentially develop the technology for use in wind turbines. The compact superconducting magnets would make wind-turbine generators cheaper and easier to manufacture. The magnets also have the potential to increase energy output from the turbine.

Coombs said the initial applications for the magnets, however, will likely be in the medical field, specifically with MRI technology.

He added that there is a great amount of interest and commercial opportunity in that market, which is worth billions of pounds worldwide.

With all MRI scanners, the magnet is the largest and most expensive component. The cheapest magnets to manufacture for MRI are resistive electromagnets, which consist of a solenoid wound from a copper wire. These magnets are rarely found in current scanners, however, because of their limited field strength and stability.

The problem, Coombs said, is that it takes roughly a couple of cubic metres of solenoid to produce a magnetic strength of 7 Tesla. Up to 9.4 Tesla is deemed safe for humans. A Magnifye superconducting magnet could produce 7 Tesla in an area that is 1in across and 0.5in deep.

'It's a much more compact source of magnetic field than a conventional solenoid so you can reduce the overall size of the superconducting magnet for MRI,' Coombs said. 'Also, it is a very local source of magnetic field so you can put lots of magnets together to make a uniform field. The manufacturing is much easier and the scanner can be made smaller, lighter and cheaper.'

Coombs said Magnifye has aspirations to commercialise its technology for electric cars, buses and even trains.

'The holy grail among motor manufacturers is to produce an electric motor which is a 10th of the size of a conventional motor and the only way of doing this is with this sort of technology,' he claimed.

Siobhan Wagner