Development of a propulsion system for a biomimetic thruster

Ngocsan Ha,Namseo Goo,Hyeonkyu Yoon

doi:10.1007/s11434-010-4134-z

Abstract

We studied theoretically and experimentally a biomimetic propulsion system inspired by the motility mechanisms of bacteria such as E. coli. Our goal was to investigate the effect of the “complex” filament of Rhizobium Meliloti bacteria on thrust force. The complex filament is a helically perturbed filament, similar to a plain filament threaded through a small helix. The propulsive performance of this system was estimated by modeling the dynamics of helical wave motion in viscous fluid. The model consists of a helical filament which is axially rotated at angular velocity ω. Resistive force theory (RFT) was applied to this model to calculate the thrust force and required torque. The Buckingham PI theorem (non-dimensional analysis) was also used to analyze the theoretical results. The procedure for making a complex filament with various pitch angles θs from a small helix and plain filament is explained in detail. To validate the theoretical results for helical wave propulsion and compare the characteristics of complex and plain filaments together, an experiment was performed to measure the thrust forces in silicone oil. The experimental results agreed with the theoretical values predicted by RFT. The thrust forces of complex filaments depended on the shape of small helix winding. The maximum thrust force was achieved at a small helix pitch angle of θs = 45°. In addition, we found that the thrust force generated by a complex filament had a value about 10% higher than that of a plain filament with the same equivalent diameter de. biomimetic micro-robots, swimming micro-robots, propulsion of flagella, medical application

Highlights

We studied theoretically and experimentally a biomimetic propulsion system inspired by the motility mechanisms of bacteria such as E. coli
We found that the thrust forces became constants beyond 55° of pitch angle, which means that the small helix did not increase the thrust force for the large pitch angle
The experimental results were shown to be in good agreement with theoretical values predicted by the Resistive force theory (RFT) model

Summary

Introduction

We studied theoretically and experimentally a biomimetic propulsion system inspired by the motility mechanisms of bacteria such as E. coli. To validate the theoretical results for helical wave propulsion and compare the characteristics of complex and plain filaments together, an experiment was performed to measure the thrust forces in silicone oil. There are several types of biomimetic swimming robots, mostly based on fin, using shape memory alloys (SMAs), ionic exchange polymer metal composites (IPMCs), and most recently lightweight piezo-composite actuators (LIPCAs) [3–7]. Most of these biomimetic robots are very effective on the macro-scale, miniaturization would make them ineffective because inertial forces become important for propulsion. Researchers investigated the fundamental fluid dynamics of a novel super-helical structure rotating in a Stokes fluid [10]

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