University of California–Riverside researchers have discovered a reliable way to incorporate color into paints, printing inks and displays—and change the color instantly, and reversibly, with magnetic fields. “For the first time, stable photonic materials with tunable colors can be fabricated on a large scale,” says Yadong Yin, an assistant professor of chemistry at UC–Riverside.
Yin and his team fabricate microscopic polymer beads that change orientation and color upon application of an external magnetic field. Researchers embed ordered magnetic iron oxide nanostructures within each microsphere. Apply external magnetic fields, and the spheres align in a different way, catching light and changing color.
The “magnetochromatic microspheres” mix well with water, alcohol, hexane and even other polymer solutions, and this stability qualifies them for a wide range of applications. The UC–Riverside team suggests re-writable signage and posters, activated security inks, environmentally friendly paints and cosmetics, and biological sensors.