Eco-friendly, highly functional materials by learning from biominerals : Imai's Group

[Aiming for eco-friendly, highly functional materials by learning from biominerals : Imai's Group]

The Imai Laboratory is researching biominerals, such as the shells and bones made by living organisms.

At present, daily life is supported by a material-based civilization, using metals, semiconductors, and plastics in particular. This places a heavy burden on the environment, by consuming lots of energy and producing lots of waste. By contrast, organisms create a variety of finely formed, highly functional materials without impacting the environment. They do this under mild conditions, at ordinary temperatures and pressures in water.

Q. Biominerals, such as shells, pearls, and human bones, are large structures made from assemblages of tiny crystals. And the structures are formed by aligning those tiny crystals, so the materials are highly functional. This has become newly clear from our research.

Q. Until now, to get a highly functional material, it was necessary to use special metallic elements. Manufacturers have had to bring lots of rare elements from various places and use those. This process can be costly, dangerous, and toxic. By contrast, we want to skillfully use familiar materials such as iron to create highly functional materials. To do this, its actually necessary to control nanostructures. By controlling and coordinating nanostructures, its possible to elicit high functionality even using the same element, by giving it a high surface area or making it highly crystalline. So its actually possible to make highly functional materials using cheap, safe metals.

To make such materials, researchers must imitate biomineral synthesis methods. Biomaterials with layered structures essentially form through self-organizing crystal growth, controlled by various organic polymers. Using special water-soluble polymers, its possible to synthesize nanostructures like those of seashells and birds eggs in water solutions.

Q. Its quite difficult to control a nanostructure while growing it. Because the techniques used by biominerals are quite sophisticated, to simply replicate them artificially in water requires quite a lot of technology and knowledge. So right now, were all doing trials. The interesting thing is that the difficult task biominerals do can sometimes be replicated comparatively simply when we grasp its essence. In this case, wonderfully precise materials can be created autonomously in a beaker. I think discovering such things is very interesting.

Q. When we become able to synthesize materials like this, firstly, energy wont be required for the synthesis. If a lot of energy is used in synthesis, a lot of CO2 and waste products are generated. By contrast, biominerals use hardly any energy. Manufacturing can be done at room temperature, without using a vacuum, high pressure, or high temperature. So manufacturing can be done using little energy under eco-friendly conditions, while producing little waste. Moreover, the synthesized materials themselves are harmless and highly functional; for example, calcium carbonate and iron oxide. So these are environmentally friendly materials.

Systems that require high crystallinity and specific surface area, such a lithium ion batteries and solar cell electrodes, sometimes correspond to biological activities. In the future, such technologies could achieve high functionality using abundant elements, like organisms do, without using wasteful amounts of energy and materials. This will lead to the development of the ultimate eco-materials, which are easily recycled and biodegradable.

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Science & Technology

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