From Gadget Lab:
Research into color-changing nanoparticles could pave the way for a new kind of display technology. A breakthrough promises tiny molecules that can change color in response to an external magnetic field that can be used to create outdoor displays and posters.
“We have developed a new way to induce color change in materials that can be fabricated on a large scale and is pretty close to commercialization,” says Yadong Yin, an assistant professor of chemistry at University of California, Riverside, who led the study that included contributions from South Korean scientists.
The technique centers on polymer beads, called magnetochromatic microspheres, which are dispersed in a liquid such as water, alcohol or hexane.
Inside the beads are magnetic iron oxide nanostructures. Changing the orientation of the nanostructures with an external magnetic field helps produce the change in color of the beads.
The process is similar to the way electrophoretic displays, more commonly known as electronic ink, work. The two systems share common properties such as being bistable (stable in two distinct states), being readable in direct sunlight and consuming very little power.
Here’s a Youtube video of the beady action. I just like the name, “magnetochromatic microspheres.”