Magnets today are made of solid, ferromagnetic metal, but that could change. Scientists have faced various difficulties designing magnets with the mechanical properties of a liquid. However, a team of scientists has now created a permanent magnetic liquid using a modified 3D printer.
While fluids with magnetic properties known as ferrofluids have been present in the world of science for a while, the newly-created magnetic liquid is different. Ferrofluids typically lose their magnetic properties in the absence of an external magnetic field, but this permanent magnetic liquid retains its capabilities without an outside magnetic field.
“We wondered, ‘If a ferrofluid can become temporarily magnetic, what could we do to make it permanently magnetic, and behave like a solid magnet but still look and feel like a liquid?'” materials scientist and engineer Tom Russell of the University of Massachusetts said in a statement. “We’ve made a new material that is both liquid and magnetic. No one has ever observed this before.”
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Despite this difference, ferrofluids and the newly-developed magnetic fluid share a lot of similarities. The permanent magnetic liquid uses iron oxide nanoparticles which are also found in ferrofluid. However, to make its magnetic properties permanent, the team developed a new 3D-printing technique which involves using liquid as a printing material. Scientists inject water into a tube of silicone oil and mix it with a nanoparticle surfactant so that it becomes more elastic. This technique serves to keep the water in one place.
The team decided to use a nanoparticle suspension only one millimeter in diameter, causing the nanoparticles to gather toward the surface of a printed droplet, creating interfacial jamming, which is a nanoparticle behavior that creates a shell at the interface between the droplets and oil suspension. They decided to magnetize it using a magnetic coil, just like ferroliquids, but when they removed the magnetic coil, the material remained magnetized.
“We almost couldn’t believe it,” Russell said. “Before our study, people always assumed that permanent magnets could only be made from solids.”
One of the biggest mysteries regarding this study is that the nanoparticles are transferring their magnetism to other nanoparticles that are free-floating inside the print droplet. This mystery allows the magnetism to remain in the material, but scientists have to explain how it happens yet.
The research described in the journal Science also found that liquids can change shapes from a cylinder-like shape to a flattened pancake and into other shapes such as a sphere and a wire.
Since the new permanent magnetic liquid can be controlled by an external magnetic field, it can be used in soft robotics, artificial cells, and much more.
“This opens the door to a new area of science in magnetic soft matter,” Russell said.