Micro- and Nano-optical Devices from Diatom Nanostructures: Light Control by Mother Nature
Natural organisms have always inspired the design and production of innovative materials, which nowadays is a new approach to innovation called biomimetics or biomimicry. Much more uncommon is the attempt to directly use parts of living organisms as technological devices. Butterfly wings, which have been used as optical gas sensors, and diatom microshells, which have been exploited in many applications as optical or electrical transducers, are among the few examples that can be found in the literature. In particular, diatoms are unicellular microalgae, whose protoplasm is enclosed in a microshell, called a frustule, made of amorphous hydrated nanoporous silica, characterized by a huge variety of morphologies and shapes, due to the over 100 000 classified species distributed in all aquatic systems. In this chapter, we will review the results of studies focused on the biophotonic properties of diatom frustules produced in our laboratories and all over the world, demonstrating how light manipulation by diatom micro- and nanostructures, made by Nature, can be effectively achieved with this low cost and largely available material.