Routing Physarum with repellents

Plasmodium of Physarum polycephalum is a single cell with many nuclei. Plasmodium is an easy-to-experiment-with biological substrate, a multi-functional bio-material used to implement novel and future computing architectures. The plasmodium exhibits typical features of excitable chemical systems and capable for distributed sensing, parallel information processing and decentralized actuation. Plasmodium of P. polycephalum is proved to be a universal storage modification machine. Actively growing zones of the plasmodium are considered to be elementary processors of the growing computing machine, as well as messages traveling in the spatially extended non-linear medium. Controlling propagation of the messages and computing processes is a prerequisite for a successful implementation of working prototypes of plasmodium machines. In laboratory experiments and computer simulation we show that active growing zones of plasmodium can be precisely routed using repelling diffusion gradients generated by crystals of sodium chloride. We demonstrate how to achieve controllable reflection, splitting/multiplication and merging of plasmodium's active zones.