New polymer that changes color instantly in response to external magnetic field.:
New polymer that changes color instantly in response to external magnetic field .
Slide 20:
Research team led by Yadong Yin Assistant professor of chemistry University of California Focused on colour changing polymer. The team has fabricated microscopic polymer beads that change colour instantly and reversibly when external magnetic fields acting upon them change orientation.
Slide 21:
Color change occurs with no change in the structure or intrinsic properties of the microspheres. What changes instead? Magnetic fields acting externally on the orientation of these microspheres. In this method, the color is tuned by changing the relative orientation of the periodic arrays in the microspheres by conveniently using external fields. Benefits? Instant action, contactless control and easy integration into electronic devices already in the market.” This is a smart and effective solution to solve the problems of previous works, which could not tune the photonic crystal structures.
Slide 22:
The color observed in the new materials is “structural color” Interference effects rather than pigments. Colorful feathers of many birds, butterfly wings and beetle shells Produced when microstructures in these objects are aligned in periodic arrays .
MECHANISM:
MECHANISM Magnetic iron oxide + resin (liquid phase) U.V radiation Dispersion Resin solid phase Mineral oil Solid microspheres Periodically arranged Spherical droplets Magnetic field U.V radiation
Slide 24:
A video showing Rotation of microspheres in a vertically changing external magnetic field. The color is switched between on (blue) and off states.
Slide 25:
The beads or “magnetochromatic microspheres” have excellent structural stability. They also are highly compatible with various types of dispersion media such as water, alcohol, hexane and even polymer solutions, allowing them to retain magnetically tunable colors in a variety of chemical environments. The new technology has a great potential for a wide range of photonic applications because the on/off switching of the diffraction color by the rotating photonic sphere is fast, greatly simplifying the pixel structures. Applications of the new material include display type units such as rewritable or reusable signage, posters, papers and labels, and other magnetically activated security features. The new material also can be used to make environmentally friendly pigments for paints and cosmetics, as well as ink materials for color printing.