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Scientists have found a way to create and cancel magnetic fields from afar.
The method involves passing electric current through a special arrangement of wires to create a file magnetic field it seems to come from another source. This illusion has real applications: Imagine a cancer drug that could be delivered directly to a tumor deep in the body capsules made of magnetic nanoparticles. It is not possible to attach a magnet to the tumor to guide the nanoparticles on their journey, but if you could create a magnetic field from outside the body centered on that tumor, you could administer the drug without an invasive procedure.
The strength of a magnetic field decreases with distance from the magnet and a theorem proved in 1842, Earnshaw’s theorem, states that it is not possible to create a point of maximum magnetic field strength in empty space.
“If it is not possible to have a maximum magnetic field in empty space, it means that it is not possible to create the field of a magnetic source remotely, without placing a [magnetic] source at the destination, “said Rosa Mach-Batlle, a physicist at the Italian Institute of Technology Center for Biomolecular Nanotechnologies in Italy who led the new research.
Related: 9 interesting facts about magnets
Making the hypothetical real
Mach-Batlle and his colleagues, however, thought they could get around the problem. They were inspired by work in optics that uses engineered materials known as metamaterials (designed to have properties not found in any natural material) to circumvent the resolution limits set by the wavelength of light. Likewise, they thought, hypothetical magnetic materials could make the impossible possible in the world of magnetic fields.
The researchers imagined a material with negative magnetic permeability 1. The magnetic permeability of a material indicates how much that material increases or decreases a magnetic field when exposed to that field. In a material with a magnetic permeability of 1 negative, the direction of the magnetism induced within the material it would be the opposite of the direction of the initial magnetic field.
Obviously, a new method for inducing magnetic fields based on materials that don’t exist would not be particularly useful. But even if this hypothetical material with negative permeability does not exist, physicists can create a kind of temporary “material” from the electric current flowing through a specific arrangement of wires. This is because current induces magnetism and vice versa, a consequence of Maxwell’s equations of electromagnetism.
Related: Magnetic fields the size of a black hole could be created on Earth, the study says
“In the end, we don’t use any material, we use a precise arrangement of the currents that can be considered an active metamaterial,” Mach-Batlle told LiveScience.
To create the remote field, Mach-Batlle and his team created a hollow cylinder consisting of about 20 wires that surround a long inner wire. As current flows through these wires, it creates a magnetic field that looks the same as if the long inner wire was actually outside the device. It is the electromagnetic equivalent of a ventriloquist casting his voice; the source of the field is not actually outside the device, but the field itself is indistinguishable from the field that would have resulted if the source were outside the device.
“We create the illusion of having this remote source,” Mach-Batlle said. The researchers published their findings on October 23 in the journal Physical Review Letters
Biomedical applications
There are still questions about how well this method might work for real-world applications. A special feature of the system is that there is an area of very strong magnetic fields between the wire barrel and the remote field. This region could interfere with some research applications, Mach-Batlle said, although it would likely be problematic or not depending on what you’re trying to do with the field.
Possible applications beyond drug delivery include canceling out magnetic fields from afar, a technique that could be useful in quantum computation to reduce the “noise” of external fields that can interfere with measurements. Another use could be the improvement of transcranial magnetic stimulation, which uses magnets to stimulate neurons in the brain to be treated. depression. Being able to control magnetic fields from a distance could improve the targeting of transcranial magnetic stimulation, so doctors can better focus on particular regions of the human brain.
Later the researchers hope to build a configuration of wires that will allow the creation of 3D magnetic fields from afar.
Originally published on LiveScience.
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