Color-Changing Photonic Fibers Created, Inspired By The Bastard Hogberry

A new type of flexible color-changing photonic fiber has been created by researchers at Harvard University and the University of Exeter. When it’s stretched, the fiber changes color, with the color varying from a deep red to a bright blue. The researchers think that the new fiber could be used for the creation of ‘smart’ fabrics that visibly change color when exposed to heat or pressure. Such fabrics could have a wide variety of potential uses.

“Our fiber-rolling technique allows the use of a wide range of materials, especially elastic ones, with the color-tuning range exceeding by an order of magnitude anything that has been reported for thermally drawn fibers,” says coauthor Joanna Aizenberg, Amy Smith Berylson Professor of Materials Science at Harvard SEAS, and Kolle’s adviser.

The fibers were inspired by the fruit of a common South American plant, the bastard hogberry. The unique structural elements in the berry’s surface layers create the bright iridescent blue color that the plant is known for.

 
“Our new fiber is based on a structure we found in nature, and through clever engineering we’ve taken its capabilities a step further,” says lead author Mathias Kolle, a postdoctoral fellow at the Harvard School of Engineering and Applied Sciences (SEAS). “The plant, of course, cannot change color. By combining its structure with an elastic material, however, we’ve created an artificial version that passes through a full rainbow of colors as it’s stretched.”

The upper cells of the seed’s skin possess a repeating ‘curved’ pattern that creates ‘color’ by interacting with light waves, somewhat similar to what gives soap bubbles color. The researchers were able to copy these key structural traits to make the new, flexible and stretchable, color-changing photonic fibers.

“For our artificial structure, we cut down the complexity of the fruit to just its key elements,” explains Kolle. “We use very thin fibers and wrap a polymer bilayer around them. That gives us the refractive index contrast, the right number of layers, and the curved, cylindrical cross-section that we need to produce these vivid colors.”

According to the researchers, the production process is easily scalable to the industrial level. It will be interesting to see what can be done with the fibers. They seem like the kind of technology that will end up having uses that are unforeseen by their creators.

The research was just published January 28th in the journal Advanced Materials.

Source: Harvard University
Image Credits: Peter Vukusic; Mathias Kolle;