Slime design: learning lessons from mold networks

Slime mold may be a pain in the home, but it turns out it can teach us how to build more effective wireless networks.

Researchers at Hokkaido University in Japan have just published the results of a study into how the mold spread. The testing was based on the idea that nature would find the most efficient way to design a network. Previous studies suggested the slime could find the quickest route through a maze.

To put the idea to a further test, the researchers used a wet surface with oat flakes placed in positions which corresponded to cities in Japan. They then placed the mold, Physarum polycephalum, in the position representing Tokyo. They also used light, which inhibits the growth of the mold, to simulate the effects of natural barriers to Japan’s railway network such as mountains.

The slime didn’t let them down. (Which is a sentence you don’t often get to write.) It spread out and created connections between the flakes which almost precisely mirrored the Japanese rail network. Analysis showed that the slime’s result had a slightly shorter total length but was also slightly less efficient.

One big drawback with the slime’s network was that its design meant a broken connection (equivalent to a faulty section of railway) was three times more likely to leave a station completely unreachable. It may be that the slime considers the risk of losing part of the organism is worthwhile for the greater good, an approach that doesn’t work so well when you have angry passengers to deal with.

What made the study particularly useful was the collection of data about how the slime network grew, something that’s difficult with an established rail network without hindsight.

The slime began by spreading out rapidly to cover the maximum surface area, in other words maximizing its chances of discovering a food source. Once it discovered food (the “stations”), it switched its focus to creating pathways between each site to speed up the process of transferring the sustenance.

The researchers have now developed a mathematical model based on the slime’s growth which they believe could be used for developing real-world networks such as those for wireless communication.

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