Inspired by natural iridescence found in butterfly wings and fish scales, the films contain an array of magnetic nanostructures which can be rotated to manipulate the reflection of ambient light.
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Ben Evans, associate professor of physics, has co-authored an article about iridescent films that can be magnetically tuned to create photonic displays.
The work was published March 19 in ACS Nano in collaboration with Zhiren Luo and Chih-Hao Chang from the Department of Mechanical and Aerospace Engineering at North Carolina State University.
ABSTRA magnetic field rotates the magnetic pillars in the array (lower panels), which changes the color of reflected light from green (top left) to yellow (top right). The mechanism mimics dynamic iridescence in fish such as the neon tetra.ACT: Inspired by the tropical fish neon tetra, we report a mechanism to achieve dynamic iridescence that can be magnetically tuned. This approach is based on the tilting of periodic photonic nanostructures, as opposed to the more common strain-induced color tuning. In this method, a periodic array of magnetic nanopillars serves as a template to guide the assembly of iron oxide nanoparticles when magnetized in a liquid environment. The periodic local fields induced by the magnetic template anchor the assembled particle columns, allowing the structure to tilt about the base when the angle of the applied field is changed. This effect emulates a microscopic “Venetian blind” and results in dynamic optical properties through structural coloration that is tunable in real time. The fabricated prototype demonstrates tunable reflectance spectra with peak wavelength shift from 528 to 720 nm. The magnetic actuation mechanism is reversible and has a fast response time around 0.3 s. This structure can be implemented on an arbitrary surface as dynamic camouflage, iridescent display, and tunable photonic elements, as well as in other applications such as active fluidic devices and particle manipulation.
