From Oats to Opal Cards: Students Map Sydney Trains with Slime

Q: What do social systems, like communities and societies, that are composed of individuals who interact and share cultures, have in common with biological systems that encompass living organisms, tissues, and organs?

A: Transport!

Just as matter, cells, and waste are transported around complex systems within our bodies, so too communities of people are moved around complex transport systems daily via train, road, sea and air.

Of course, social and biological systems have another thing in common: ways to think around problems whether together or as a collective. This intersection of science and society was explored by Year 10 students in Term 1 2025, with a group of budding young scientists keen to explore how the slime mould Physarum polycephalum could form networks with comparable efficiency, fault tolerance, and cost, to those of real-world infrastructure networks—in this case, the Sydney rail system.

They were inspired by a team of researchers from Japan and the U.K. who in 2010 fed a slime mould with nutrients arranged to imitate the nodes of the Tokyo subway system. The resulting network was strikingly similar to the real thing, and sparked the emergence of what is now known as biologically inspired adaptive network design.

In its vegetative phase, the slime mould Physarum polycephalum ‘slimes’ its way through the world seeking food. As it explores, it links previously found food sources with tubular structures. When food sources were deposited on a plate in a pattern corresponding in miniature to the positions of the cities that surround Tokyo, the resulting network of Physarum tubules that developed was similar in structure to the railroad network that connects the Japanese cities.

This biologically inspired model has since provided insight into how to implement properties like resistance of transport systems to local failures into similar human-designed systems.

“We had to disinfect all the materials, then put agar on the petri dishes for the slime mould (Physarum polycephalum purchased on the internet), and then we put oat flakes in places to mimic the shape of the Sydney train system,” explained Thomas Ko (10We).

“We printed out maps and put the flakes on main stations such as Strathfield, Redfern, Parramatta and the Sutherland Shire. We had around 11 stations,” added Isaac Chan (10WH).

Like all great experiments, the boys learnt that many variables can impact outcomes, particularly infection control when it came to cleaning hands after eating! “It took a couple of goes: the slime mould died on our first attempt; and then it also got infected with bread mould, which may have been due to cross contamination,” Isaac admitted.