Slime molds

04 Apr 2022

Slime molds are single cell organisms which you can see with the naked eye. Although not having a brain, they have what is known as the most primitive form of intelligence and memory, being able to solve mazes and control robots. I want to make a robot controlled by the slime mold, but in order to do so i’ll first study their behavior.

Experiment 1: (IR-)light

Knowing they don’t like visible light, how do slime molds react to infrared? To test this i made a simple circuit, connecting a IR-LED to a 9v battery. First i calculated the resistance needed to connect an IR-LED to a 9v battery.

Then i soldered the circuit. To see if the mold preferred darkness over IR, we taped part of the petri-dish containing the molds. We used two petri-dishes with molds to lower the chance of a random/false result. Together with the IR we put the molds in a box to check on them in a couple of days.


The result wasn’t the result i expected! I expected the molds disliking the IR light, or not responding to it at all. Instead one of the slime molds completely moved to the side with IR. The other mold didn’t respond to it at all.

(left: mold didn’t respond, right: mold moved to IR side completely)

This could have multiple reasons. The left petri-dish only has a single layer of tape, maybe the IR light past trough the tape. Also, the white tape + the plastic of the petri-dish could reflect the IR, so the tape didn’t prevent the IR coming in.

To do: Same experiment, but with black tape to avoid reflection. Maybe a smaller area with IR to see if they are really attracted to IR.

Experiment 2: (IR-)light 2.0

I recreated the previous experiment to rule out any random results. I replaced the 9v battery and prepared 3 petri-dishes with slime-molds, agar and oats. I taped of different sections. I also ensured that the inside of the tape was black to avoid light bouncing/reflecting.


The section with the black X is the taped section.

The molds don’t seem to react on IR light. In al the 3 petri-dishes the molds moved to both the taped and untaped section. I think it’s save to say slime-molds don’t mind IR-light.