title: Transfer function of protoplasmic tubes of Physarum polycephalum.
abstract: The slime mould Physarum polycephalum is a large single celled myxomycete; its plasmodium consists of tubes which extend to find sources of food. It has been previously shown that the tubes are conductive with a resistance of approximately 3 MΩ, and have been used in basic DC circuits. Hybrid slime mould-electronic circuits have been proposed, using the protoplasmic tubes, grown between agar, as Physarum wires. This paper aims to evaluate the electrical properties of the protoplasmic tubes with respect to analogue and digital waveforms. The Physarum wires act as low pass filters with a mean cut off frequency of 19kHz (SD 9 KHz); they have a 12.1 dB/decade roll-off (SD 1.9 dB/decade). Mean attenuation across the band-pass range is -6 dB (S.D. 4.5 dB). The mechanism for the frequency dependant attenuation is unknown however a combination of protoplasmic electrolyte and the cytoskeletal structure is the most likely cause. The tubes last approximately 2 weeks before forming a dry sclerotia, when they cease being conductive and is the prevalent limiting factor of their practical use; this is caused by dehydration and lack of nutrition, a limitation which may be overcome. The potential for Physarum wires in hybrid circuits is strengthened; while previous circuits were simple DC circuits, this work demonstrates that they may be used as electronic components or wires in both digital and analogue circuits or even as a computing component in analogue computers.
authors: International Centre of Unconventional Computing, University of the West of England, Bristol, BS16 1QY, UK. Electronic address: James.whiting@uwe.ac.uk.
authors: James G H
authors: JG
authors: Whiting
authors: International Centre of Unconventional Computing, University of the West of England, Bristol, BS16 1QY, UK; Institute of Biosensor Technology, University of the West of England, Coldharbour Lane, Bristol, BS16 1QY, UK.
authors: Ben P J
authors: BP
authors: de Lacy Costello
authors: International Centre of Unconventional Computing, University of the West of England, Bristol, BS16 1QY, UK.
authors: Andrew
authors: A
authors: Adamatzky
mesh_terms: D000362:Agar; D003593:Cytoplasm / Q000378:metabolism*; D004553:Electric Conductivity; D016839:Physarum polycephalum / Q000378:metabolism*
chemical_list: D000362:Agar
keywords: Biological electronics; Frequency response; Passive filter; Physarum wires