A Soft Pneumatic Maggot Robot

Drosophila melanogaster has been studied to gain insight into relationships between neural circuits and learning behaviour. To test models of their neural circuits, a robot that mimics D. melanogaster larvae has been designed. The robot is made from silic

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School of Informatics, Institute of Perception, Action and Behaviour, University of Edinburgh, Edinburgh EH8 9AB, UK [email protected], [email protected] School of Engineering, Scottish Microelectronics Centre, University of Edinburgh, Edinburgh EH9 3FF, UK [email protected]

Abstract. Drosophila melanogaster has been studied to gain insight into relationships between neural circuits and learning behaviour. To test models of their neural circuits, a robot that mimics D. melanogaster larvae has been designed. The robot is made from silicone by casting in 3D printed moulds with a pattern simplified from the larval muscle system. The pattern forms air chambers that function as pneumatic muscles to actuate the robot. A pneumatic control system has been designed to enable control of the multiple degrees of freedom. With the flexible body and multiple degrees of freedom, the robot has the potential to resemble motions of D. melanogaster larvae, although it remains difficult to obtain accurate control of deformation.

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Introduction

We have designed a robot to mimic Drosophila melanogaster larvae (maggots), as a platform to test and verify their learning and chemotaxis models. Drosophila as a model system has a useful balance between relatively small number of neurons yet interestingly complex behaviours [10]. Many genetic techniques, such as GAL4/UAS systems developed by Brand and Perrimon [2], facilitate research on the connectivity and dynamics of the circuits. As a result, a number of necessary components of neural circuits for sensorimotor control and learning are being found and modelled. Currently, the models are tested by comparing between wildtype and genetic mutation lines, or using simulations of neural circuits and comparing output with biological experimental recordings. To test models in a wider environment, more similar to a larva, a physical agent that copies properties of the larval body is important. Larvae have high degrees of freedom (DOFs) and flexible bodies. As a result, they are able to do delicate and spatially continuous motion. Simplified in mechanics, a larval body consists of body wall attached to the muscles and body fluids inside the body wall. The 2 parts works together as a hydrostatic skeleton [5]. The skin has regular repeating symmetrical folds, which are essential for its deformation and friction, forming its segments. The muscles of Drosophila larvae are in 3 orientations: dorso-ventral, anterioro-posterior and c Springer International Publishing Switzerland 2016  N.F. Lepora et al. (Eds.): Living Machines 2016, LNAI 9793, pp. 375–386, 2016. DOI: 10.1007/978-3-319-42417-0 34

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oblique. Antero-posterior muscles are located nearer the interior than dorsoventral muscles. The body wall muscles are segmentally repeated, and in each abdominal half segment there are approximately 30 of them ([1]) (Fig. 1).

Fig. 1. A Drosophila larva expressing mCherry (a type of photoactivatable fluorescent proteins [14]) in its muscles. From Balapagos (2012).

Based on the property of