A team of researchers at Peking University has used the wings of cicadas as stamps to pattern polymer films with nanometre-sized structures.
Cicada wings are characterized by highly ordered arrays of closely spaced microscopic pillars. When these wings are pushed down on a smooth polymer film, they create a negative imprint of the array pattern.
Professors Jin Zhang and Zhongfan Liu and their colleagues from Peking University and Nanotechnology Industrialisation Base of China made the discovery. They found that the insect wings possess sufficient rigidity and chemical stability and have a low enough surface tension to be used as stamps to pattern polymer films on silicon substrates. A low surface tension is necessary so that the wings do not stick to the substrate and can be released without destroying the imprinted structures.
The wings have a waxy coating gives these structures the low surface tension which makes them ideal for use as stamps. An ordered array of microscopic wells can be obtained on the polymer film by using the pillar array on the wings. This pattern can be transferred to silicon by an etching process, leading to the formation of ‘nano-wells’ on a silicon chip.
Silicon wafers patterned with ‘nano-wells’ show promising anti-reflective properties. Arrays of microscopic gold pillars can also be obtained by using the imprinted moulds. These pillar arrays are almost exact replicas of the structures found on the insect wings and may be useful for optical imaging or the detection of molecules by Raman spectroscopy.
‘This technique is a powerful demonstration of how natural nanostructures existing in the environment can be used to pattern microscopic structures not easily accessible by conventional microfabrication technology’, said Zhang. ‘There is a lot that nature can teach us about nanotechnology’, added Liu, citing examples of butterfly wings and lotus leaves, which are characterized by exquisitely ordered arrays of microscale and nanoscale structures.