Abstract

The slime mouldPhysarumpolycephalumis a suitable candidate organism for soft-matter robotics because it exhibits controllable transport, movement and guidance behaviour.Physarummay be considered as a smart computing and actuating material since both its motor and control systems are distributed within its undifferentiated tissue and can survive trauma such as excision, fission and fusion of plasmodia. Thus it may be suitable for exploring the generation and distribution of micro-actuation in individual units or planar arrays. We experimentally show how the plasmodium ofPhysarumis shaped to execute controllable oscillatory transport behaviour applicable in small hybrid engines. We measure the lifting force of the plasmodium and demonstrate how protoplasmic transport can be influenced by externally applied illumination stimuli. We provide an exemplar vehicle mechanism by coupling the oscillations of the plasmodium to drive the wheels of a Braitenberg vehicle and use light stimuli to effect a steering mechanism. Using a particle model ofPhysarumwe show how emergent travelling wave patterns produced by competing oscillatory domains may be used to to generate spatially represented actuation patterns. We demonstrate different patterns of controllable motion, including linear, reciprocal, rotational and helical, and demonstrate in simulation how dynamic oscillatory patterns may be translated into motive forces for simple transport of substances within a patterned environment.

Highlights

  • Very small scale mechanisms made possible by recent advances in micro-fabrication still require a means of energy conversion to convert a fuel supply into useful motive force

  • We suggest that the myxomycete organism, the true slime mould Physarum polycephalum, is a suitable candidate organism which meets both criteria; i.e. it is a complex organism, but which is composed of relatively simple materials

  • Due to the relatively slow time development of the Physarum plasmodium and natural variability of its ‘performance’ in terms of the chosen robotics tasks, it is helpful to develop computational modelling approaches which may facilitate the study of distributed robotic control

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Summary

Introduction

Very small scale mechanisms made possible by recent advances in micro-fabrication still require a means of energy conversion to convert a fuel supply into useful motive force. A giant single-celled organism, Physarum is an attractive biological candidate medium for emergent motive force because the basic physical mechanism during the plasmodium stage of its life cycle is a self-organised system of oscillatory contractile activity which is used in the pumping and distribution of nutrients within its internal transport network. In this report we discuss the use of Physarum as a candidate organism and material for the spontaneous generation and distribution of physical forces for engine-like and distributed planar transport mechanisms.

Experimental
Cell shape and oscillation pattern
Force Generated by Plasmodium
Steering control of Physarum engine
Vehicle simulation driven by experimental data
The emergence of oscillatory transport phenomena in a particle-based model
Model setup
Data analysis
Results
Transport motion in open ended patterns
Transport in closed path patterns
Conclusion and discussion

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