Tuesday, 19 March 2013

Bio-inspired optical fibers change color when stretched

Inspired by nature, materials scientists at Harvard University (Cambridge, MA) and the University of Exeter (Exeter, England) have invented a new fiber that changes color when stretched. The researchers identified and replicated the unique structural elements that create the bright, iridescent blue color of a bastard hogberry—a tropical plant’s fruit. The multilayered fiber could be used in smart fabrics that visibly react to heat or pressure.

Principal investigator Peter Vukusic, associate professor in Natural Photonics at the University of Exeter, and his collaborators at Harvard studied the structural origin of the seed’s vibrant color. They discovered that the upper cells in the seed’s skin contain a curved, repeating pattern, which creates color through the interference of light waves.

The team’s analysis revealed that multiple layers of cells in the seed coat are made up of a cylindrically layered architecture with high regularity on the nanoscale. The team replicated the key structural elements of the fruit to create flexible, stretchable, and color-changing photonic fibers using an innovative roll-up mechanism perfected in the Harvard laboratories. The fibers’ superior mechanical properties, combined with their color brilliance and tunability, make them very versatile. For instance, the fibers can be wound to coat complex shapes. Because the fibers change color under strain, the technology could lend itself to smart sports textiles that change color in areas of muscle tension, or that sense when an object is placed under strain as a result of heat. Contact Mathias Kolle at mkolle@seas.harvard.edu.

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