But now, researchers at Lawrence Berkeley National Laboratory have managed to create the first permanently magnetic liquids, which could open up new avenues for electronics and robotics.
Ferrofluids have been around since the 1960s, and since then they've shown up in speakers, eye-catching clocks, surfaces that can change their stickiness or slipperiness on demand, and may soon be used to propel small satellites. But in all these cases, the liquid only shows magnetism when a magnetic field is applied. The Berkeley Lab's new liquid is the first to be permanently so.
"We've made a new material that is both liquid and magnetic," says Tom Russell, lead researcher on the study. "No one has ever observed this before. 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'?"
The team started by 3D printing 1-mm droplets of a ferrofluid, each of which contained billions of iron-oxide nanoparticles just 20 nanometers wide. These were suspended in another liquid solution. On closer inspection, the researchers found that the droplets retained their shape because the nanoparticles were crowding around the edges.