Lodestone, a naturally occurring iron oxide, was the first permanent magnetic material known to man. The Han Chinese used it for divination of boards 2200 years ago; The ancient Greeks wondered why iron was attracted to it. and Arab merchants put it in water bowls to observe the magnet point on the way to Mecca. Today, scientists have used magnets to read and record data on hard drives and create detailed images of bones, cells and even atoms.
One thing has remained constant in this story: our magnets are made of solid materials. But what if scientists could make magnetic devices out of liquids?
"We made a new material that has all the characteristics of a common magnet, but we can change its shape and adapt it to different applications because it's a liquid," said Thomas Russell, a polymer scientist at the University of Massachusetts, Amherst, and the lead author of the study. "It is very unique."
With a special 3D printer injected Dr.. Russell and his colleagues from the Lawrence Berkeley National Laboratory use iron oxide nanoparticles in droplets of toluene a colorless liquid that does not dissolve in water. The team also added a soap-like material to the droplets and then suspended them in water.
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The soap-like material aggregated the iron oxide nanoparticles on the surface of the droplets to form a semi-solid shell. "The particles remain stuck in place like a jam at 5 o'clock," Dr. Russell.
Next, the scientists placed the droplets on a stir plate with a rotating bar magnet and observed something out of the ordinary: The positive and negative poles of the liquid magnets followed the external magnetic field through the fixed magnet, causing the droplets on the plate to dance. When the solid magnet was removed, the droplets remained magnetized.
"We almost could not believe it," Dr. Russell.
In the 1960s, NASA scientists discovered that some liquids could be magnetized in the presence of a strong magnetic field. However, these fluids known as ferrofluids always lose their magnetism as soon as the stronger external magnetic field is removed.
By contrast, droplets produced by Russell and his team become magnetic and remain so thanks to the nanoparticle shell that forms in the soap emulsion.
The drops can be shaped with little effort, as if a traffic cop encounters this traffic jam and sets things in motion. Russell.
The movement of liquid droplets can also be controlled with external magnets. For example, liquid magnets may be useful for delivering medication to specific locations in a person's body and for developing "soft" robots that can move, change shape, or grasp things.
and think about new applications for liquid magnets, "Dr. Russell. "Because people in materials science have not thought that this is possible."