Towards Physarum Engines

TL;DR

This paper explores how Physarum polycephalum can be shaped and controlled to create micro-actuators and engines, demonstrating oscillatory transport, force generation, and steering mechanisms for soft robotics applications.

Contribution

It introduces experimental methods to shape Physarum for controllable oscillatory behavior and demonstrates its use in driving vehicle mechanisms and generating actuation patterns.

Findings

Physarum can produce controllable oscillatory transport behaviors.

External illumination influences protoplasmic transport.

Simulated patterns show potential for diverse motion types.

Abstract

The slime mould Physarum polycephalum is a suitable candidate organism for soft-matter robotics because it exhibits controllable transport, movement and guidance behaviour. Physarum may 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 of Physarum is 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 of Physarum we 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.