Modelling mycelium growth

 

Why material science?

Since material names are used to define periods of civilisations of the past (Stone Age, Bronze Age, etc ...), material science is considered, in my opinion, one of the species-defining endeavours. Civilizations that mastered smelting iron ended up victorious. All of a sudden, enemies had to deal with stronger swords and implantable shields. The same applies today, countries that managed to master silicon chip manufacturing ended up economically victorious.

With the advent of biotechnology, largely with the help of artificial intelligence tools such as AlphaFold, there could be a promise of a new class of materials that are grown instead of manufactured. Bio-composite materials offer an alternative solution to create materials inspired by nature and can returned to it at the end of their lifespan. Such materials will tremendously accelerate reaching our sustainability goals.

Mycelium Composites

One such material is mycelium, which is considered nature's solution to the recycling issue. Mycelium is the fine network of filament of tiny threads called hypha usually found underneath the soil surface. It is considered part of fungi, the other visible part is of course the mushroom body (Figure 1). When used with organic matter placed in a mold, mycelium acts as a binder holding the organic matter (substrate) tightly to form a rather strong material with impressive mechanical properties (figure 1). Moreover, you can tune these properties to suit your desired application, from leather to thermal insulation to packaging material. One such company doing this is BiodesignSA.

Figure 1

Back to Turing

In order for a material to be taken seriously by engineers and designers, they need to be able to predict its behaviour. Biology is notoriously complicated, but computation efforts and AI can help us find solutions. In a previous post, I showed how Turing's reaction-diffusion model can help predict communication between cells for morphogenesis to occur. Here, I show how can that same model be used to predict mycelium growth in a substrate. As a teaser, here's how you could use the simulations to imagine how mycelium growth will look like given substrate positioning.

via GIPHY

If you saw the word "Bio", yes that is what it was supposed to be

Model setting up

The model was inspired by a paper called " The origins of Spatial Heterogeneity in vegetative mycelia: a reaction-diffusion model" by C.M. Regalado and others. It hypothesises an interaction of activators and inhibitors similar to how Turing imagined in his paper, with the addition of another crucial component, the substrate. A system of PDE system is developed that hopefully shows the interaction between mycelium hypha and the substrate.

If you want to understand reaction-diffusion models in general, refer to my previous post here. I used VisualPDE to simulate the model and it is very interesting! Below, you can try this model by clicking anywhere. By clicking, you're increasing the substrate concentration in that specific area (i.e. increasing variable s in the model). What is being viewed below is the activator, which is an indication of mycelium growth. I recommend pressing the restart button before adding the substrate. Have fun!