Chinese scientists have developed miniscule capsules that alter color on application of a magnetic field. When the capsules are arrayed, magnetic fields can be applied to produce colored patterns economically.
Some animals make small physical changes at their surface or skin to alter the wavelength of light in order to change colors. The researchers mimic this act by utilizing standard clusters of compact spheres called as colloidal crystals. The interval between the spheres’ center decides the wavelength of the reflecting light and thus the crystal’s color. By adding fluid or increasing the dimension of the spheres, color of the crystals can be changed.
If magnetic spheres are utilized, the color change can be done by applying a magnetic field to alter the intervals between the spheres. By utilizing this method, the color noticed varies with the viewing angle and unable to produce stable systems. Zhongze Gu and his colleagues at the Southeast University in Nanjing have developed stable droplets of particles with wide range of color tuning options independent of the position of the viewers.
The researchers have arrayed bunches of magnetic spheres in a liquid inside compact, visible resin beads that are homogeneous and can be used as pixels individually in an exhibit. The magnetic spheres inside the capsules move closer together or further apart depending on the type of magnetic fields applied, producing variety of colors.
Uniform composition and sizes are essential if these materials are to be utilized as displays, for which scientists have utilized microfluidic techniques to develop the capsules. In the microfluidic techniques, reactions happen constantly as reactants journey via the ultra compact reactor’s narrow channels. By altering the flow rates of the reactants, the shape, shell thickness and size of the capsules can easily be controlled. By utilizing electronic magnetic fields, the compact size of the microcapsules can produce more interesting and difficult color patterns.