Slime mould Physarum polycephalum is a large single celled organism1 whose amorphous body is able to form complex, optimised networks of protoplasmic tubules between spatially distributed nutrient sources. It has been demonstrated that the organism’s natural foraging behaviour may be characterised as distributed sensing, concurrent information processing, parallel computation and decentralized actuation2,3,4,5. The ease of culturing and experimenting with P. polycephalum makes this slime mould an ideal substrate for real-world implementations of unconventional sensing and computing devices2. A range of hybrid electronic devices have recently been implemented as experimental working prototypes. They include self-routing and self-repairing wires6, electronic oscillators7, chemical sensor8, tactical sensor9, low pass filter10, colour sensor11, memristor12,13, robot controllers14,15, opto-electronic logical gates16, electrical oscillation frequency logical gates17, FPGA co-processor18, Shottky diode19 and transistor13.#R##N##R##N#Several challenges still remain towards fabricating functionally useful slime mould computing devices. For example, the live substrate’s inherent variability renders cascading of various varieties of logical gate too unreliable for constructing complex computing circuitry. We detail here the creation of laboratory prototypes of functional, reliable electrically-coupled discrete and sequential logical devices that utilise slime mould as circuit elements. This was achieved through characterising bioelectrical output of slime mould protoplasmic tubes in response to an insulting stimulus—localised heating. This rationale was based on the principle that the organism is able to isolate portions of its body (transiently and permanently) in response to harmful stimuli by ceasing the rhythmic movements of cytoplasm through certain anatomical regions—which usually serves to distribute the contents of the cell and contribute to the production of motive force—hence isolating them from metabolically active regions of the cell. Isolated protoplasmic tubes have a significantly higher electrical resistance than their unaltered counterparts20, which provides a basis for distinguishing between logical states when monitoring bioelectrical activity.
['Xavier Alexis Walter', 'Ian Horsfield', 'Richard Mayne', 'Ioannis Ieropoulos', 'Andrew Adamatzky']
On hybrid circuits exploiting thermistive properties of slime mould