A new material derived from a dazzling fish that can quickly change colours could be ideal for camouflage technology.
Nature continues to inspire a whole range of advanced technologies, particularly in the areas of materials science and aerospace. One of the latest creations comes from North Carolina State University, where a team of researchers is drawing inspiration from the tiny neon tetra fish with the hope of tapping into its ability to control its brightly coloured stripes by changing the angle of tiny platelets in its skin.
In a paper published to ACS Nano, the team revealed it had replicated this process to create a new material that can shift its colour by using a magnetic field to change the orientation of an array of nanocolumns. The material consists of four layers, including a silicon substrate coated with a polymer that has been embedded with iron oxide nanoparticles.
The polymer incorporates a regular array of micron-wide pedestals, making the polymer layer resemble a Lego brick. The middle layer is an aqueous solution containing free-floating iron oxide nanoparticles, held in place by a transparent polymer cover.
When a vertical magnetic field is applied beneath the substrate, the floating nanoparticles are pulled to align over the pedestals. In doing so, the researchers can change the orientation of the nanoparticle columns, shifting the wavelength of light most strongly reflected by the material and thereby changing its colour. This resulted in the material morphing rapidly from a dark green colour to neon yellow.
“Next steps for us include fine-tuning the geometry of the column arrays to improve the purity of the colours,” said Chih-Hao Chang, corresponding author of the study. “We are also planning to work on the development of integrated electromagnets that would allow for more programmable colour shifts.”
Along with potentially creating new camouflage technology, the researchers also see a future for its use in reflective displays.