The Nanotechnology in Butterflies
The branch of Nanotechnology is fast becoming a frenzied topic amongst both experts and laypersons alike. Whilst it seems to be burdened with misunderstandings and over expectations, its progress and place in our everyday lives is inevitable. Nanotechnology is already changing the way we live, and it’s only the beginning (Rogers, Adams & Pennathur, 2013). As nanotechnology is defined by size, it becomes an incredibly broad branch of science and, in turn, provides opportunity for breakthroughs amongst a great number of scientific fields. Our current knowledge and experience of this unique Nano-world is limited, however, Mother Nature provides an abundance of nanostructures that can be used as inspiration (Huang, Wang, & Wang, 2006), for instance, the Blue Morpho Butterfly. The Nano structure of these butterfly wings hold ability to be water repellant, whilst maintaining vibrant colours to aid in the intimidation of predators. The research into these interesting properties, is allowing insight on how we are able to replicate them for our own use. This review will discuss the structure of the butterfly wing and the interesting colour properties that result. An overview of the structure’s application toward anti-counterfeiting will also be addressed.
The structure of butterfly wings
The Nano structure behind the brilliance of butterfly wings is not dissimilar to that of the lotus plant’s, however; the structure utilized is slightly varied. The process behind the creation of the butterfly’s colorful wings is quite unique, consider that most objects absorb and reflect light as determined through use of pigments. The colour of butterfly wings is produced by the structure that makes up their wings. Layers of scales that, when examined under an electron microscope, are said to be covered in additional structures that resemble Christmas trees (Starkey, 2005). Each of these structures contains eight or nine layers separated by air gaps; an arrangement which is known as a photonic crystal; a material consists of structures with a size similar to the wavelength of the incident ray, which traps light within it thereby only allowing certain wavelengths to pass through.
These Nano-sized ridges and holes, refract, diffract and reflect light to create their luminous colour. A direct effect of this diffraction is the wing’s apparent ability to change colour depending upon the light source and viewing angles. The colour that is then reflected from the wing is determined by the constructive and destructive interference caused by the ridges, or in other words the alignment of the scales and the distances between the layers. Additionally, the structure of the scales creates a hydrophobic surface. This surface allows the butterfly’s wings to repel water which is significant in the ability to maintain it’s flight capacity as well as deter any bacteria or fungi (Karthick, & Maheshwari, 2008), thereby reducing the likelihood of contracting infection or disease. The absence of pigments, or chemical properties, in the coloration of butterfly wings adds to the appeal where its colour will not fade over time due to the unchanging nanostructure of the wing.
In terms of applications, a current talking point is utilizing the structure within butterfly wings to create an effective anti-counterfeiting method where an etching, replicating the structure to that of a butterfly wing, can be inscribed into an abundance of materials. Unlike holograms, which require addition of dyes and pigments, the Nano approach to counterfeiting merely subtracts, drilling Nano-holes into it to reflect light (Tossell, 2013). The way that it works is that microscopic gratings (creating ridges) composed of nanostructures interact with light to produce the same shimmering iridescence. These structures will act to diffract light to produce the signature blue wings of the Morpho Butterfly and absorb other unnecessary light (Butterfly wings behind anti-counterfeiting technology, 2011). This reduces the chances of a surface not being compatible with this technology, creating use upon a variety of items including bank notes, passports and pharmaceuticals. Additionally, it may be able to be used to authenticate legal documents, or be read by machines for use on information disks such as CDs. Tossell (2013) says that to create an ideal anti-counterfeiting product it needs to be difficult enough to keep highly skilled and well funded counterfeiters at bay, as well as be simple enough to produce in bulk in order to keep affordability for customers.
Until recently, replicating the complex surfaces of butterfly wings has been technologically unimaginable, where the structures for producing such intense colours are precise to one billionth of a meter include repetitive patterns of air space and cuticle. Knowledge and research toward the structure of the butterfly’s wing has enhanced the outlook towards the future of anti-counterfeit devices where these artificial structures have the ability to be used to encrypt information within colourful signatures to protect passports, bank notes and other items from forgery.
Huang, J., Wang, X., & Wang, Z. L. (2006). Controlled replication of butterfly
wings for achieving tunable photonic properties. Nano Letters, 6(10), 2325-2331.
Retrieved from http://pubs.acs.org.ezproxy.ecu.edu.au/doi/abs/10.1021/nl061851t
Karthick, B., & Maheshwari, R. (2008). Lotus-inspired nanotechnology applications. Resonance, 13(12), 1141-1145. Retrieved from http://link.springer.com.ezproxy.ecu.edu.au/article/10.1007%2Fs12045-008-0113-y
Rogers, B., Adams, J., Pennathur, S. (2013).Nanotechnology: The whole story. Boca Raton, Fl: CRC Press.
Starkey, A. (2005). The butterfly effect. New Scientist,187(2518), 46.
Tossell, I. (2013, April 1) Famous butterfly inspires anti-counterfeit nanotechnology. The Global and Mail. Retrieved from http://www.theglobeandmail.com/report-on-business/small-business/starting-out/famous-butterfly-inspires-anti-counterfeiting-nanotechnology/article10600835/