Bio-inspired fibres change colour when stretched

A team of materials scientists at Harvard University and the University of Exeter has invented a new fibre which changes colour when stretched.

Inspired by nature, the researchers identified and replicated the unique structural elements, which create the bright iridescent blue colour of a tropical plant's fruit. The multi-layered fibre, described in the journal Advanced Materials, could lend itself to the creation of smart fabrics that visibly react to heat or pressure.

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

Since the evolution of the first eye on Earth more than 500 million years ago, the success of many organisms has relied upon the way in which they interact with light and colour, making them useful models for the creation of new materials. For seeds and fruit in particular, bright colour is thought to have evolved to attract the agents of seed dispersal, especially birds.

The fruit of the South American tropical plant, Margaritaria nobilis, commonly called ''bastard hogberry,'' is an intriguing example of this adaptation. The ultra-bright blue fruit, which is low in nutritious content, mimics a more fleshy and nutritious competitor. Deceived birds eat the fruit and ultimately release its seeds over a wide geographic area.

''The fruit of this bastard hogberry plant was scientifically delightful to pick,'' says principal investigator 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.''