| There can be few flowers as well-known as the | | | | radiation. |
| Edelweiss, but few would think to look to this woolly | | | | Ultraviolet radiation is best known for causing sunburn, |
| white, Alpine flower for a source of technological | | | | snow blindness and skin cancer in people, but it also |
| inspiration. Now, however, scientist Jean-Pol Vigneron | | | | damages a wide range of materials, including fabrics, |
| of the University of Namur in Belgium and his | | | | paints and plastics. "Finding ways to absorb damaging |
| colleagues in Budapest, Meise and Stanford think they | | | | ultraviolet radiation is a common engineering problem," |
| may have found just that. | | | | comments Prof Vigneron, " so we were excited to |
| When the researchers investigated the micro-structure | | | | see a plant that has developed a clever solution to this. |
| of Edelweiss flowers, last January, they were | | | | We immediately thought this structure would be very |
| surprised to find a peculiar ultra-violet-absorbing | | | | useful for anti-U.V.-coatings for specialist car- and |
| structure in the dense white hairs, which cover the | | | | aircraft-paints, as well as sunscreens and anti-U.V. |
| whole Edelweiss plant. The hairs are especially | | | | packaging materials. The problem was how to |
| abundant on the modified silver-white leaves that form | | | | manufacture artificial fibres with such miniscule |
| the Edelweiss's "flowers". Vigneron and his fellow | | | | diameters as those found in the Edelweiss." The |
| scientists immediately realized that there would be a | | | | scientists soon realized, however, that by copying the |
| wide variety of commercial uses for synthetic versions | | | | Edelweiss structure in glass, they could borrow |
| of the structure, but the prospect of actually | | | | manufacturing techniques developed to make optics |
| manufacturing Edelweiss-inspired structures seemed | | | | fibres and dramatically simplify the process. |
| remote. | | | | Optic fibres are made from large glass rods, called |
| "We found that the surface of each hair is covered in | | | | "preforms", a few inches in length and about one inch |
| tiny, regularly spaced fibers, running parallel to each | | | | in diameter, which are stretched ("pulled") at both ends |
| other along the length of the leaf hairs," explains | | | | until a thin fibre 10,000 times longer and correspondingly |
| Vigneron. "Each fibre is just 180 millionths of a millimetre | | | | thinner is produced. Interestingly, the thin fibres have the |
| in diameter. Because of their small size and highly | | | | same shaped cross-section as the original rod, to an |
| regular arrangement, these fibres together made up a | | | | accuracy of a few percent. The researchers realized |
| structure, which absorbs ultraviolet light. It does not | | | | it would be possible to copy the exact shape of the |
| affect visible light at all because it has longer | | | | Edelweiss fibres and turned to their partners at the |
| wavelengths than ultraviolet, so is not disturbed by the | | | | PHLAM laboratory in Lille, France, to discuss the |
| structure. With mathematical modeling techniques, we | | | | technical details of producing prototypes. For the |
| were able to show that when ultraviolet waves fell on | | | | French laboratory ( which belongs to a |
| the structure, they were guided by it and eventually | | | | waveguide-developing company), the scientist's plans |
| absorbed, either within the walls of the hairs or, | | | | have proven surprisingly simple to carry out and it |
| possibly by a material in the middle of the hairs." | | | | plans to begin production of some artificial Edelweiss |
| The scientists were able to check their calculations by | | | | fibres in October. |
| taking measurements of how much of the light falling | | | | Currently, most products offering protection against |
| on the silver-white Edelweiss leaves was reflected, | | | | U.V. use tiny spherical "nanoparticles"of Titanium |
| and how much was transmitted and passed through | | | | dioxide, which are effective, but can be difficult to |
| them. Sure enough, they found that very little of the | | | | arrange on a surface. The project organizers hope |
| ultraviolet light falling on the plant was reflected or | | | | that the synthetic Edelweiss fibres will provide the |
| transmitted, instead, it was almost all absorbed by the | | | | same level of UV protection as the nanoparticles but |
| hairs covering the leaves, just as their mathematical | | | | be easier to handle. |
| model had predicted. The hairs seem to protect the | | | | The research described was published in Volume 71 of |
| plant leaves beneath them from damaging U.V.A. | | | | Physical Review E. |