Fruit of the “bastard hogberry” plant.
Inspiration can strike from the unlikeliest of places. Take the amusingly named bastard hogberry plant, for instance. Indigenous to South America, the fruit of the Margaritaria nobilis evolved its vibrant blue hue to entice birds to gobble it up and facilitate the dispersal of its seeds over a wide geographic area. By identifying and replicating the structural elements responsible for the fruit’s color, scientists from Harvard University and the University of Exeter managed to invent a new kind of photonic fiber that shifts from red to blue—and several colors in between—when subject to pressure.
The resulting multilayer fiber, as described in this month’s issue of Advanced Materials, could lead to the creation of smart fabrics that visibly react to heat or pressure, such as athletic-wear that changes color in areas of muscle tension or strain.
“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. “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 multilayer fiber could lead to the creation of smart fabrics that visibly react to heat or pressure.
After studying the structural origin of the seed’s iridescence, the team at Harvard discovered that the upper cells in the seed’s skin contain a curved, repeating pattern that creates color through the interference of light waves. (A similar mechanism is responsible for the way soap bubbles glisten.) Further analysis revealed that multiple layers of cells in the seed coat are each made up of a cylindrically tiered architecture with high regularity on the nanoscale.
It was by replicating these key structural elements that the scientists were able to create a flexible, stretchable, and color-changing fiber using an inventive “roll-up” technique they perfected in the Harvard labs.
“The fruit of this bastard hogberry plant was scientifically delightful to pick,” says Peter Vukusic, associate professor in natural photonics at the University of Exeter. “The light-manipulating architecture its surface layer presents, which has evolved to serve a specific biological function, has inspired an extremely useful and interesting technological design.”