Magnetochromatic Material Changes Color on Command

Spinning magnetic microspheres creates instant color changes and rewritable displays

Rotation of microspheres in a vertically changing external magnetic field. The color is switched between on (blue) and off states. Video courtesy Yin lab, UC Riverside

In the future, signs will be instantly rewritable and walls will change color at the flip of a switch. A research team at the University of California at Riverside has created a new magnetically activated, instantly and reversibly color-changing material with potentially groundbreaking applications. The technology is based on that used by colorful birds, beetles, and butterflies: instead of static pigments, the material employs "structural color," which depends on the interference effects of light.

Although other methods for creating tunable structural color exist, their color-changing processes are slow and complicated, and involve internal adjustments. This new material is composed of microscopic polymer "magnetochromatic microspheres," or beads, whose structural stability allows for instant changes in color with "no change in the structure or intrinsic properties of the microspheres themselves," according to Yadong Yin, who led the study.

The beads' colors change in response to magnetic fields, which alter the relative orientation of the periodic arrays within them. This use of magnetic fields allows for "instant action, contactless control, and easy integration into electronic devices already in the market."

The color-changing beads can also be used to create environmentally friendly pigments for inks and paints. Yin, an assistant professor of chemistry, and his colleagues, plan to work next on the wide array of applications for which this material is so promising. "Rewritable energy-saving display units such as papers and posters are our main interests," says Yin in the announcement. "We will also try to develop a similar new material for chemical and biological sensors."