Slime mold (Physarum polycephalum): A paradigm for self-assembly of robust networks. Background and motivation

Resource distribution networks play a crucial role at all scales of biological and artificial systems. Within an individual organism, cells receive nutrients and expel waste. Nutrients must be transported from a source to all cells efficiently. Similarly, waste must be collected from every cell and transported out of the organism. Communities of organisms and entire ecosystems have the same requirements and natural selection drives the system to create efficient resource distribution networks. Artificial resource distribution networks such as our transportation system or our utility grid, rely upon a top-down design paradigm where a designer or team of designers lay out the network using the best analytic methods available. Sometimes these methods are rudimentary or even irrational. Modifications are made in an ad-hoc manner as needed. For instance, if one is building a new housing development, one builds a road connecting to the existing network. Unfortunately, a top-down management approach to a complex system which is not understood becomes meaningless. In recent years, there has been a drive to design and implement biologically-inspired systems. Resource distribution networks are nothing new in the natural world. One encouraging observation is that very simple life forms are capable of developing efficient and robust resource distribution networks. Physarum polycephalum is one such organism. Physarum polycephalum is a single-celled organism that we can grow in colonies in theMEC Lab. The colony requires only nutrients (oat flakes), moisture, warmth and air to thrive. Moisture is supplied by the agar medium on the petry dish. Warmth and air are controlled at a constant value in the lab. The controllable variable is the quantity and location of the food. These single-celled creatures decide to form distribution tubes. Central issues