A material which should not be very useful in practice, but which constitutes a promising proof of concept.
Spider silk is well known to naturalists and engineers for its exceptional resistance. At equal diameter, these fibers can be up to five times stronger thansteel !
Obviously, these properties are of great interest to researchers; in materials science, spider silk is an inexhaustible source of inspiration. Science has already made some great discoveries by trying to reproduce its structure. This is how, in 2018, Professor Fuzhong Zhang and his team at Washington University in St. Louis succeeded in making a bacterium produce a recombinant spider silk, with performance similar to the real material. This gave the researcher an idea: by pushing the same structural recipe further, would it be possible to create a material that performs better than spider silk?
According to the latest work published by him and his team in ACS Nano, it would seem that the answer is a big “Yes”. They present a fiber “amyloid polymer”Stronger than Kevlar, and even stronger than some natural bristles.
The well-kept secrets of eight-legged engineers
To achieve this result, the researchers had to overcome a large number of obstacles. In particular, the most difficult was to solve the problem of β nanocrystals. These structures are one of the main components of spider silk; despite their small size, these crystals are directly responsible for the resistance of the wire. However, the recipe for cooking a spider’s web is extremely precise; if the fiber contains too few of these crystals, it loses its properties and disintegrates.
The concern is that while our eight-legged friends obviously master the manufacturing process, humans don’t. “Spiders know how to weave fibers with a precise quantity of nanocrystals”, explains Zhang. “But when humans weave it artificially, the amount of nanocrystals is often too low.”.
To solve this problem, the researchers had an idea: they made the fiber produced by a genetically modified bacteria. To do this, they isolated the part of the spider genome corresponding to the formation of silk, which they transferred to a bacterium. They introduced a sequence capable of generating a somewhat peculiar structure, called a sequence. amyloid. There are several types, but what they have in common is that they allow certain proteins to form. fold and clump; in this case, this results in the formation of the desired β nanocrystals.
Take inspiration from nature to do better than it does
The fibers in question are unlikely to be of much use as they are. On the other hand, they represent a very interesting proof of concept; by thus combining a principle of bioengineering with a natural matrix, it would be possible to produce many materials with exceptional properties. “It demonstrates that we can rework biology to produce materials that beat the best materials in nature.”, Explains Zhang.
This opens up a whole field of still unexplored possibilities in terms of high performance engineering. Because among the thousands of amyloid sequences referenced by chemists, this study only explored three! It is therefore quite possible, and even “probable”According to the authors, that other even more efficient combinations are hidden in nature … and with them, so many new potential breakthrough materials.
The text of the study is available here.