Liquid magnets made possible by Berkley lab 3D printing

Terminator 2's fearsome T-1000

Terminator 2's fearsome T-1000

Because of nanoparticle-polymer mix interactions, the resulting ultra-soft droplet has magnetic properties similar to solid magnets but with liquid characteristics. This could include artificial cells that can deliver targeted cancer therapies, or flexible liquid robots that can change their shape to adapt to their surroundings. Russell is the head of a program called Adaptive Interfacial Assemblies Towards Structuring Liquids.

Prof Russell said: "These incredible liquid magnetic materials will attract attention in biology, physics and chemistry". "No one has ever observed this before", explained Russell. Based on these special physical properties, ferrofluids are already used in electrical devices, medical applications, mechanical engineering and materials science research, he notes. "Before our study, people always assumed that permanent magnets could only be made from solids", said Russell.

The study published on Thursday in the journal Science described the one-millimeter droplets made from a ferrofluid solution containing billions of iron-oxide-nanoparticles just 20 nanometers in diameter. To make the particle magnetic, the team placed the droplets by a magnetic coil solution, and the magnetic coil pulled the nanoparticles towards it. However, when the coil was removed, the droplets kept their magnetism permanently, while gravitating towards each other in ideal unison, in what the scientists described as an "elegant swirl" or "little dancing droplets".

Next, the team passed a magnetic coil over the droplets, which fired up their magnetism. GIF via Xubo Liu/Berkeley Lab.

This means that by applying an external magnetic field, scientists can control liquid devices made this way, like waving Harry Potter's wand, he suggests, "which opens promising research and application areas such as liquid actuators, liquid robotics and active-matter delivery". With just 8 nanometers between each of the billion nanoparticles, together they created a solid surface around each liquid droplet.

Key to this finding were the iron-oxide nanoparticles jamming tightly together at the droplet's surface.

Upon magnetization, the jammed nanoparticles at the solid surface transfer their magnetic orientation to the particles at the core, thus enabling the whole droplet to become permanently magnetic. On nearer inspection, the researchers discovered that the droplets retained their form because the nanoparticles were crowding around the edges.

Among the magnetic droplets' many incredible qualities, what stands out even more, Russell noted, is that they change shape to adapt to their surroundings. Now, usually all the magnetic devices that produce magnetic fields are composed of solid materials, however, the latest innovation a team of scientists at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) makes use of liquid for magnetic devices.

"What began as a curious observation ended up opening a new area of science".