Experiment: The Lego Maze Challenge

One of the most famous experiments in biology proved that a single cell could solve a maze.

In 2000, researchers at Hokkaido University showed that Physarum polycephalum could connect two food sources in a maze using the shortest possible distance. Now, you can run the same experiment at home using standard toys from your closet.

Why it works: The Slime Memory

When the blob moves, it leaves behind a trail of transparent slime. It hates moving back over its own old slime. This creates a “physical memory” that tells the blob where it has already searched, allowing it to “calculate” the most efficient route without a brain.

Phase 1: The Build

1. Design the Maze: Build a small maze out of standard Lego® bricks on a flat plastic baseplate.
2. The Substrate: Prepare your Non-Nutrient Agar (mix the powder with distilled water, boil, and let it cool slightly).
3. The Fill: Pour the liquid agar into the lanes of your Lego maze until they are about half-full (approx. 5mm deep). Let it cool and solidify into a jelly.
4. Darkness: Make sure you have a lid or a box to keep the maze in total darkness.

Phase 2: The Invasion

1. Add the Blob: Use sterile tweezers to place a piece of active yellow blob at the “Entrance” of the maze.
2. The Wait: Let the blob explore. Over the next 12-24 hours, the blob will grow until it fills virtually every lane of the maze. This is normal! It is “scouting” its territory.

Phase 3: The Challenge

1. The Food: Place one oat flake at the Start and another at the Finish (or any two points in the maze).
2. The Transformation:
   • Within hours, the blob will detect the chemical signature of the oats.
   • It will begin to speed up the pulses in the veins that connect the two oats.
   • It will retract its protoplasm from the dead ends.
   • The Result: You will be left with one single, thick yellow cable connecting the two oats via the shortest possible path.

Cleaning Up (Biological Safety)

After your experiment, don’t just throw the maze in the dishwasher!

• Lego Safety: Soak your Lego blocks in 70% Isopropyl Alcohol or a weak bleach solution (10% bleach, 90% water) for 15 minutes. This kills any remaining spores.
• Washing: Scrub them with a soft brush to remove the agar and slime trails, then wash with standard soap.
• Warning: Never boil or autoclave Lego blocks. They will melt and turn into a colorful plastic puddle.

What’s Next?

Think your blob is a genius? Try the Tokyo Subway Map experiment next to see how it designs efficient transport networks.