Magnetochromatic Beads

The beads or "magnetochromatic microspheres" have excellent structuralstability. They also are highly compatible with various types ofdispersion media such as water, alcohol, hexane and even polymersolutions, allowing them to retain magnetically tunable colors in avariety of chemical environments.

"Unlike many conventional approaches, the instantaneous color changeoccurs with no change in the structure or intrinsic properties of themicrospheres themselves," said Yadong Yin, an assistant professor of chemistry who led the study that broughttogether chemists at UCR and engineers at Seoul National University,South Korea. "What changes instead are the magnetic fields actingexternally on the orientation of these microspheres, these photoniccrystals. Our work provides a new mechanism for inducing color changein materials. Now, for the first time, stable photonic materials withtunable colors can be fabricated on a large scale."

Applicationsof the new material include display type units such as rewritable orreusable signage, posters, papers and labels, and other magneticallyactivated security features. The new material also can be used to makeenvironmentally friendly pigments for paints and cosmetics, as well asink materials for color printing.

"Within a certain range, it is possible also to tune the color of the material by simply rotating the microspheres," Yin said.

Source: photonics.comAdded: 24 June 2009