11 Aug 2008
Nanostructured lens copy is a candidate for compact imagers and tiny optical sensors.
Biotemplating experts based in Spain and the US have reproduced a fruit fly's compound eye in chalcogenide glass – a material with excellent infrared optical properties and good mechanical durability. Pleased with the result, the team is now busy exploring a wide range of uses for its ultra-compact lens (Nanotechnology 19 355704).
"Since the compound eyes of flies are very efficient collectors of light, their replicas could also be used to fabricate solar-cell covers and other energy-harvesting structures as well as lenses offering good spatial resolution," Akhlesh Lakhtakia of Penn State University told nanotechweb.org. "The development of compound-eye-based miniature cameras and optical sensors could stimulate applications in automobile engineering, credit cards, security and surveillance, displays, and medical technology."
To overcome the considerable challenge of reproducing tiny curved surfaces and hard to reach embedded features, the team uses a method dubbed conformal-evaporated-film-by-rotation. The oblique angle deposition technique works by directing a vapour flux towards the target substrate at an angle of 85°. During deposition the substrate holder is rotated at a speed of 0.5–2.0 revolutions per second.
The method creates an actual replica of the template rather than an inverted structure. Once coated, the biotemplate is removed using a plasma ashing process to leave a standalone copy.
"We can work with infrared transparent materials, such as chalcogenide glasses, to produce infrared microlenses and visible laser-hardened infrared sensors, as well as photodiodes, solar sensors, solar concentrators, photonic crystals, optical bioprobes and so on," commented Lakhtakia on behalf of the team. "We expect one of the first applications to involve the efficient collection of solar energy in solar cells. Another early application is likely to be high-resolution lenses."
Using the same technique, the group has also replicated microelectronic circuits in various materials.