Complex nanostructures can be built from solutions containing nucleic acids. Photo courtesy of photocase.com

In the last few years, development in nanotechnology has enabled us almost literally to construct new molecules by using individual atoms as building blocks in an ‘atom by atom’ approach. This opens up a unique opportunity for designing completely new chemical and material products with a high degree of control of the emergent functional properties.  Biological molecules are especially attractive for the nanoscientists as building blocks due to their spatial complexity, their self-assembling properties and the many diverse ways in which biological molecules can be assembled. In a new paper, scientists from the Russian Academy of Science show that the most promising building blocks are the nucleic acids found for instance in DNA. Their superior properties include their difference in length from a few nucleotides to chains several of micrometres long, the ability of the nitrogen bases to chemically react with a  long host of other compounds and of course the ability of strands of nucleic acids to bond with other strands of nucleic acids to form complex three-dimensional structures.

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Bombardier beetles belong to the family Carabidae (ground beetles). More than 500 species are described world wide. Shown here is a bombardier beetle from the genus Brachisinus. Photo taken by Patrick Coin (from Wikipedia).

The bombardier beetles have long fascinated scientists and natural historians alike due to their extraordinary line of defence against predators such as ants, frogs and birds. When threatened, they squirt a hot stream of liquid chemicals onto their aggressor accompanied by a loud popping sound. The chemicals, hydroquinones and hydrogen peroxide, are secreted by a pair of glands. Each gland consists of a reservoir and a reaction chamber connected by a valve. The reaction chamber is connected to the outside world via a nozzle and an exit valve. The reservoir contains an aqueous solution of hydroquinones and hydrogen peroxide, while the reaction chamber is filled with a mixture of catalase and peroxidases dissolved in water. Muscles squeeze the content of the reservoir into the reaction chamber, where extremely fast reactions occur. These reactions results in free oxygen and generate enough heat to bring the liquid to the boiling point. The valve to the reservoir closes due to the pressure of the released gasses and the liquid is expelled explosively through the nozzle and exit valve at the tip of the abdomen. By rotating the abdominal top, the beetles can aim the nearly boiling liquid in any direction. A direct hit is fatal for other insects and can cause considerable pain even in humans.

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An artistic impression of a self-moving endoscope in the human intestine. Courtesy of BIOLOCH

This story, allegedly true, illustrates nicely the method which researchers have called biomimetics – an imitation of mechanisms found in nature. Today this process, from studies of nature to the finished technological product, has been formalised and professionalized. Now the process is most often conducted as a collaboration between biologists and engineers in interdisciplinary centres and research groups.

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A Morpho butterfly, with the characteristic blue iridescent colour. Courtesy of Photocase.com.

These effects have applications in a wide range of areas including the counterfeiting industry, in cosmetics and in paints. Traditionally biomimetic photonic crystals have been made by focused ion beam chemical vapour depositions. A method that relies on powerful ion beams to irradiate vapour free nitrogen radicals and other compounds at high temperatures onto a surface and thereby slowly building up the structure. This method, however, is very costly and thus only commercially relevant for production of very expensive nanostructures...

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