Oat flakes are commonly fed to Physarum to act as chemoattractants and orient the critter’s growth. They’re also the main food sources employed in the making of living wires.
However, I regularly experience issues in attracting the slime mold to its food source. Sometimes, of course, the slime mold does get to the bare oat flake and colonizes it, as this picture shows (with an oat flake stuck underneath the electrode to see how the slime mold would behave without the presence of agar):
But on other plates, the slime mold visits the new oat flake quickly, colonizes it and retracts its connection tube, leaving a white trace of slime between the blobs! And that’s when it got there, as I sometimes see it growing not toward the oat flake, but away from it:
What can be done with this?
I’ve found this paper written by James G.H. Whiting, Ben P.J. de Lacy Costello and Andrew Adamatzky, which discusses different “chemical inputs” and maps out their effects on the slime mold’s electrical activity. At page 11-12 of 18, the authors observe that:
The results of the agar attractant experiment show that 2% agar is not a strong attractant, as it only attracted the Physarum in 22% of the time. The 6% agar is more of an attractant than just pure water, due to the frequent migration from a pure water source to a 6% agar gel, supporting the hypothesis that at certain concentrations, agar can be an effective attractant.
One solution, then, could be to prepare 6% agar blobs to better attract the slime mold tubes, and keep trying!