Car Paint That Copies Butterflies

RESEARCHERS AT NISSAN MOTOR CO. LOOKED CLOSELY AT the wings of a South American butterfly and got the inspiration for a car paint that will never fade. The iridescent blue of the Morpho Sulkowskyi is produced by the way tiny structures in the wing scales refract, diffract, and scatter sunlight (photo, above). A Nissan group led by senior research engineer Hiroshi Tabata found tightly spaced grooves about 1.8 microns deep. Each groove is lined with even tinier horizontal ridges called lamalla, which are packed together like louvers about 0.15 micron apart--half the width of the lines on the most advanced computer chips (electron microscope image, left).

In an early effort, Nissan researchers added iridescence to the paint on some 1991 and 1992 models of the luxury Infiniti by adding particles of graphite to conventional paint pigments. Now, Nissan hopes to do away with pigments entirely. Instead, cars would be covered with polymer fibers that have surface microstructures similar to those on the wing scales of M. Sulkowskyi. Nissan's plan is to squeeze the polymers out of microscopic nozzles. The sun's ultraviolet rays cause conventional pigments to decay, but a car coated with the butterfly-inspired paint would give off its color as long as the microstructure remains intact. Tabata hopes to have a prototype in three or four years.

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