Biomimetics of photonic nanostructures

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Biomimetics of photonic nanostructures
Biomimetics is the extraction of good design from nature. One approach to optical biomimetics focuses on the use of conventional engineering methods to make direct analogues of the reflectors and anti-reflectors found in nature. However, recent collaborations between biologists, physicists, engineers, chemists and materials scientists have ventured beyond experiments that merely mimic what happens in nature, leading to a thriving new area of research involving biomimetics through cell culture. In this new approach, the nanoengineering efficiency of living cells is harnessed and natural organisms such as diatoms and viruses are used to make nanostructures that could have commercial
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Here, plastic sheets bearing the anti-reflector were attached to each interior surface of triple glazed windows using refractive-index-matching glue to provide a significant difference in reflectivity. Today the moth-eye structure can be made extremely accurately using electron-beam etching7 (Fig. 1c), and is used commercially on solid plastic and other lenses. A different type of anti-reflective device, in the form of a sinusoidal grating of 250 nm periodicity, was discovered on the cornea of a 45 million-year-old fly preserved in amber8 (Fig. 1b). This type of grating is particularly useful where light is incident at a range of angles (within a single plane, perpendicular to the grooves of the grating), as demonstrated by a model made in a photoresist using lithographic methods8. Consequently it has been used on the surfaces of solar panels, providing a 10% increase in energy capture by reducing the reflected portion of sunlight9. Again, this device is embossed onto plastic sheets using holographic techniques. Many birds, insects (particularly butterflies and beetles), fishes and lesser-known marine animals exploit photonic nanostructures on their surfaces to make their colour change with viewing angle (iridescence) and/or appear ‘metallic’. These visual effects appear more pronounced than those produced by

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