The delicate mushrooms served on a hamburger, or the tender, springy mushroom caps adorning the logs in the forest, are not distinguished by strength or hardness on the outside. But their distant fungal relative, Fomes fomentarius, may hold the key to producing new materials that could replace modern plastics.
This fungus, which resembles a horse’s hoof, can be found on continents around the world, and it attaches itself to damaged tree bark as a pathogen that causes diseases such as white rot. Fomes fomentarius has long been used as tinder (any material that ignites from a single spark) fungus and even to make plant-based artificial leather, but now a team of researchers in Finland has found that this resilient fungus could open the way to bio-derivatives plastics that imitate its structure.
Due to its unique combination of properties, Fomes fomentarius “could offer a great source of inspiration for producing multifunctional materials with superior properties for diverse medical and industrial applications in the future,” the study said. The fungus can be used to develop durable products such as bulletproof vests, aircraft exoskeletons or windshield coatings.
“There is a huge variety of solutions to different material engineering problems in nature, and not all of them have yet been properly explored,” said Pezhman Mohammadi, senior author of the paper and scientist at VTT Technical Research Center of Finland, in an email to Motherboard. “We were interested in the origin of the good material properties of the Fomes fomentarius fungus.”
The study of the components of fungi, such as mycelium (the network of fungal filaments) or chitin, which is a component of the cell walls of fungi, is already well underway. Mycelium is being studied for its potential as a building material on Earth, and chitin for its potential as a building material on Mars.
To determine how the Fomes fomentarius could remain lightweight but strong enough to hold onto a tree, the researchers used chemical and mechanical analysis tools such as computed tomography, X-ray diffraction, and infrared spectroscopy to peer inside the fungus and determine its structure. The results of the research were published in the Science Advances journal.
In their analysis, the team discovered that the fungus is made of three distinct layers: a hard, outer crust, a foam-like layer called ‘context’, and a section of tightly packed hollow tubes called hymenophore tubes (H. tubes).
Despite the fact that all three layers are mainly composed of mycelium and other similar chemical components, the difference in the microstructure and density of the layers creates excellent mechanical properties. According to Mohammadi, this characteristic is crucial because it shows how small changes in the mushroom-based material can create a variety of properties without having to create new materials from scratch to achieve them.
Another unusual feature the team discovered while studying the fungus was its ability to remain lightweight while providing strength on par with much heavier materials.
“To increase the strength of materials, compromises usually have to be made, for example by increasing the density,” Mohammadi said. “[Yet] when comparing the material properties of F. fomentarius structures, it is important to consider how light they are compared to hard plastic or wood. For example, hymenophore tubes are comparable in strength to wood, but are much lighter than wood.”
An important first step toward the mushroom-coated future will be for scientists to understand how the fruiting body — the part of the mushroom that we can see — is created from spores. So far it has not been studied in laboratory conditions.
Mohammadi hopes that until then, these new findings will continue to fuel interest in living materials such as fungi.
“Collaboration will allow these discoveries to be used to develop, for example, the next generation of programmable materials capable of sensing, learning, self-repairing and adapting to different situations,” he said.
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