Magnetic resonance – from surgery to space

Magnetic resonance – from surgery to space

A small set of metal jaws like clamps are in place. Gently grasp the patient’s gallbladder. But the handheld device isn’t physically connected to anything – it appears to be floating inside the person’s body.

In reality, the jaws are controlled remotely by a robotic arm that uses special magnets.

“We can see the critical structure, the blood vessels,” said Dr. Matthew Kroh of the Cleveland Clinic in Ohio. Soon he had removed the problematic gall bladder with the help of his robot assistant. This is one of two dozen or so similar surgeries he and his team have performed in recent months using their high-tech system.

“It allows us to perform very common operations in a less invasive way,” he said, explaining that fewer incisions are now needed for procedures like this. But there are many emerging applications that also use carefully manufactured magnets.

Permanent magnets, the kind that keep colorful souvenirs stuck to your fridge door, may seem like a relatively mature and established technology. After all, they have been used for centuries. Today, however, researchers and companies are working hard to make magnets more powerful and efficient than ever before.

This is because, more and more, magnets are being used in all kinds of emerging technologies – including EV motors and wind turbines. Therefore, they are essential for electrification. However, magnets are usually made using rare earth elements, the result of dirty mining operations. And, currently, China largely dominates global permanent magnet production, with more than 90% market share.

Many argue that we need cleaner, more widely distributed magnet manufacturing facilities. The future, they say, depends on it.

“My job is brilliant,” says Matthew Swallow, technical product manager for Bunting Magnetics in the UK. “No one else, I don’t think, is involved in much.”

His firm makes magnets used in all kinds of systems – from cochlear implants, to emergency brakes on rollercoasters, including at Alton Towers. Bunting Magnetics has even supplied magnets to Nasa.

Mr Swallow says that, even in the last 10 years or so, the availability of high-grade magnets made with the rare earth element neodymium has improved. For such magnets designed to withstand temperatures up to 200C, grade N35 is used to be the maximum. But now N52 grade version is commercially available.

“You can literally make a magnet 60% smaller and get the same level of performance,” Mr Swallow explained.

In an electric motor, a magnetic field helps the internal coil rotate. This might be used to drive the axles and turn the wheels of an electric car, for example. Higher grade magnets mean a motor that runs more efficiently and a car that weighs a little less overall. The careful addition of small amounts of dysprosium, another rare earth element, is one way to increase the magnet’s efficiency.

One reason why China dominates global production of these magnets is financial incentives, said Ross Embleton, senior analyst for metals & mining – rare earths at Wood Mackenzie. Rare-earth permanent magnets are subject to a 13% VAT discount on exports from the country, and regional governments provide support for energy costs, for example, which also help boost magnet-making facilities.

“It’s a really challenging industry to compete in if you’re outside of China,” Mr Embleton said.

That doesn’t stop some from trying. US firm Niron Magnetics says it has succeeded in making good quality magnets without rare earths. Instead, they use iron and nitrogen to make iron nitride magnets. This depends on getting the iron nitride to take on a certain crystal structure, which generates a magnetic field.

Chief executive Jonathan Rowntree declined to explain his company’s production techniques in detail, but he said Niron had produced magnets that worked. The first of these will be used in speakers.

Magnetic field strength is measured in terms of teslas, and Niron magnets are now at one tesla. Mr Rowntree says you can make far more powerful magnets, up to 2.4 teslas, with iron nitride.

Alternatively, recycled magnets would also be better for the environment than making new rare earth magnets from scratch.

In the UK, the University of Birmingham has developed a method to extract rare earth alloys from old electric motors and computer hard drives, for example.

A spin out company, HyProMag, has now successfully extracted rare earths using the technology, and aims to begin commercial production of magnets using the material later this year.

Meanwhile, US firm Noveon Magnetics said it had developed its own method for recycling magnets. When asked about the process, and the grade of magnet produced, chief commercial officer Peter Afiuny declined to elaborate, except to say that a small amount of alloy was mixed with recovered material to achieve the desired result. The entire process is approximately 40% more efficient than traditional virgin magnet production.

It can be difficult to tell the quality of old magnets from unused consumer electronic devices, however, Mr. Embleton said. And sometimes magnets get stuck to products with hard epoxy resin, making them difficult to remove.

But gradually, as the initial generation of EV motors and wind turbines reach the end of their lifespan in the coming years, more magnetic materials are expected to become available for recycling.

“There was a bit of a delay there waiting for the material to come back,” Mr Embleton said. Companies have the opportunity to perfect their recycling processes in the meantime.

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