Colour change

A research team led by a chemist at the University of California, Riverside has fabricated microscopic polymer beads that change colour instantly and reversibly when external magnetic fields acting upon the microspheres change orientation.

The beads, or ‘magnetochromatic microspheres’, have excellent structural stability.

They are also compatible with various types of dispersion media such as water, alcohol, hexane and even polymer solutions, allowing them to retain their magnetically tuneable colours in a variety of chemical environments.

'The instantaneous colour change occurs with no change in the structure or intrinsic properties of the microspheres,' said Yadong Yin, an assistant professor of chemistry, who led the development that brought together chemists at UCR and engineers at Seoul National University, South Korea.

To fabricate the microspheres, the researchers first mixed magnetic iron-oxide particles into a resin, which is initially in liquid phase but later turns solid on exposure to ultraviolet curable resin.