The sea sponge will help create a new class of eco-materials
An international research team, which includes a biologist from St Petersburg University, has performed an experiment in which they exposed the skeleton of a sea sponge to high temperatures. As a result, these scientists obtained a graphitic, porous structure that can be used to create new, environmentally friendly materials.
Extreme biomimetics (or biomimicry) is a whole new field of interdisciplinary research with tremendous promise. What it has to offer is in demand in the most diverse fields, from medicine to nano- and space technologies. Researchers who apply this scientific method produce synthetic materials that simulate the properties of those found in nature. A perfect example of biomimetics in action is research into sea sponges. Over the 600 million years of their existence on Earth, these animals have learned how to synthesise a skeleton ranging from centimetres to metres in size, and they have survived many natural disasters.
The main component of a sea sponge’s skeleton (spongin) may hold the key to the production of renewable, nontoxic and degradable organic structures that can take the place of many environmentally unfriendly materials. Spongin consists of keratin, just like the hair, horns and nails of other animals, and is capable of withstanding high temperatures, up to 360 °C when there is oxygen available and up to 1200 °C when there is not. It is also resistant to acid attack, and, as a result, spongin shows great promise as a source of raw materials for the production of composite materials.
Carbonation – aeration at a high temperature – enhances the durability of spongin for industrial use. In recent experiments, when heated up to 650 °C, it has shown high mechanical and chemical durability. This has prompted researchers to come up with even stronger carbonated structures from spongin.
They have put it into a smelting furnace heated up to 1200 °C. This temperature converts other biological materials, such as silk or human collagen, into coal dust. In experiments, however, after being in a furnace for an hour, though it lost 70 percent of its volume, spongin completely retained its micro- and nanostructure. As a result, scientists have been able to cut various figures out of it. Further study of spongin has shown that, while it preserves its appearance, it turns into porous graphite.
When heated, in an anoxic environment, even up to very high temperatures, spongin preserves the molecular motif in the structure of its connective tissue. Scientists believe that this makes it possible to suppose that a sponge’s skeleton could withstand an even higher temperature, turning into crystallised carbon without losing its structure.
Research into spongin was initiated by Hermann Ehrlich, the founder of extreme biomimetics and a professor at the Institute of Electronic and Sensor Materials, the Freiberg University of Mining and Technology in Germany. Such extensive interdisciplinary research is impossible to conduct at a single laboratory. For this reason, Professor Ehrlich has assembled an international team from the science and technology laboratories of different universities in Germany, France, Poland, the USA, Slovakia and Russia. This research is supported by the Russian Science Foundation (Project No 17-14-01089).
Since I have turned out to be the lone expert on the biology of sponges (the phylum Porifera) in this international team, one of my contributions to the research has been the general biological description of the samples and the analysis of the findings, again, from a biological perspective. In addition, my role in the experiment has involved the ultrastructure research, above all with the help of transmission electron microscopy.
Aleksandr Ereskovskii, Doctor of Biology and Professor at St Petersburg University (Department of Embryology)
According to Professor Ehrlich, the strong nanoporous material with a large surface area that came about as a result of the research is very suitable for the production of chemical catalysts. After thermal evaporation was performed on copper, a copper-carbon catalyst was produced that is mechanically strong and chemically stable in both salt and fresh water. It purifies the water of 4-nitrophenol, a toxic substance that is used in the manufacture of different chemical and pharmaceutical products and ends up in water with other industrial waste. In experiments using a catalyst to decontaminate water, the 4-nitrophenol was completely gone within two minutes. Scientists hope that this catalyst will find many uses in chemical research and in manufacturing.