Motor Protein Inspired “Artificial Muscle” Actuator A THESIS SUBMITTED TO THE SCIENCE AND ENGINEERING FACULTY OF QUEENSLAND UNIVERSITY OF TECHNOLOGY IN FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE BY RESEARCH Benjamin Alan Rudder School of Chemical, Material and Structural Engineering Science and Engineering Faculty Queensland University of Technology 2017 Copyright in Relation to This Thesis c Copyright 2017 by Benjamin Alan Rudder. All rights reserved. Statement of Original Authorship The work contained in this thesis has not been previously submitted to meet requirements for an award at this or any other higher education institution. To the best of my knowledge and belief, the thesis contains no material previously published or written by another person except where due reference is made. QUT Verified Signature Signature: Date: March 2017 i To my family ii Abstract The replacement, augmentation and imitation of human skeletal muscle is a narrow and specific area of study with broad implications. With the rise in demand for exoskeleton structures and aids, this technology becomes ever more relevant. Currently, however, existing systems are inadequate or have severe drawbacks in general and especially when applied to skin-contacting applications, such as high operating temperatures, voltages, and currents. There is also a lack of a more faithful adaptation or biomimicry of muscle to the bionics field. The foundation is laid for a new form of artificial muscle, which more closely mimics the structure of skeletal muscle down to its most basic units myosin and actin motor proteins. An electro-mechanical drive method together with the geometrical properties of the sarcomere, aims to create an efficient, safe, and low temperature device which can be implanted or be in contact with skin. The feasibility of the principle is investigated, physical size limitations of each of the working elements (including micromagnets and electromagnets) ascertained, and two (larger scale) prototypes produced. A numerical simulation is also developed to enable optimization through refining the design with further conditions. The biological analogies are explored and scalability discussed, in order to develop expan- sion from sarcomere level, to myofibril, muscle cell, and whole muscle level. These areas of investigation provided improvements and have presented a feasible new paradigm for the development of more biologically inspired and efficient artificial muscles, which relies on minimisation to improve efficiency and strength. Further research is required and development is in progress, but the results and idea are exciting and promising. iii Keywords Sliding filament theory, QUT, Artificial Muscle, Actuator iv Acknowledgements I would like to express my appreciation for the following people and organisations; each instru- mental in the completion of this work: • My QUT supervisors: Professor Cheng Yan and Dr Wijitha Senadeera for their endless patience, stern encouragement, and professional manner. • Dr. rer. nat. Oliver Schwarz, from Fraunhofer Institute for Manufacturing Engineering and Automation IPA and Universitat Stuttgart, with whom I began this journey and who put me on the path of this project with the initial area, and my inspiration towards biomimetics. • QUT’s Science and Engineering Faculty and Higher Degree Research staff and manage- ment, who allowed me the flexibility and freedom to make my mistakes and learn new things. In addition, I would like to show my appreciation for the support of my family and friends throughout this extended study, for both distracting me and focusing me when I needed it, and for being ever patient, understanding, and loving. There are many stories and many individuals, I cannot list you all here. Finally, this chapter is closing. v Table of Contents Abstract iii Keywords iv Acknowledgements v List of Figures xi List of Tables xii 1 Introduction 1 1.1 Motivation and significance . 1 1.2 Background . 1 1.3 Thesis Outline . 3 2 Literature Review 5 2.1 Muscles . 5 2.1.1 Definition . 5 2.1.2 Power density of muscle . 6 2.1.3 Myosin, Actin and the Sliding Filament Theory . 6 2.1.4 Action potential . 11 2.2 Existing Artificial Muscle Systems . 11 2.2.1 Fluidic Muscle . 11 2.2.2 Shape Memory Alloy . 12 2.2.3 Piezo Systems . 16 2.2.4 Electroactive Polymers . 22 vi 3 Fundamental Theory of Motion Realisation 27 3.1 Magnetics . 27 3.1.1 Basic Principles . 27 3.1.2 Magnetic Regions . 28 3.1.3 Landau-Lifshitz Energy Equation . 28 3.1.4 Single Domain Particles . 29 3.1.5 Magnetic Materials . 30 3.2 Electromagnets . 31 3.2.1 Basic Principles . 31 3.2.2 Equations . 31 3.2.3 Amperes law . 31 3.2.4 Biot-Savart law . 32 3.2.5 Dipole-dipole equations . 33 3.2.6 Micro-scale coils . 33 3.3 Nano- and Micro-system construction . 34 3.3.1 MEMS . 34 3.3.2 Manufacture Methods . 34 3.4 Macro-scale Materials . 38 4 Design Concepts and Process 41 4.1 Ring field . 41 4.1.1 Difficulties . 41 4.2 Stepping arms . 43 4.3 Parallelisation and Series . 46 4.4 Control . 47 4.5 Physical Calculations . 47 4.5.1 Qualitative Dimensional Analysis of Electromagnet . 47 4.6 Qualitative Design of Arm elements . 50 vii 5 Prototyping 54 5.1 Sarcomere Model . 54 5.1.1 Concept . 54 5.1.2 Manufacture . 61 5.1.3 Testing . 65 5.1.4 Results . 67 6 Conclusions 73 7 Future Work 73 References 81 viii List of Figures 1.1 Simplified depiction of the Sliding Filament action . 2 1.2 Cyclic Depiction of the Sliding Filament Theory . 3 2.1 Organisation of skeletal muscle[5] . 7 2.2 Sarcomere detail . 7 2.3 Sarcomere bands explained [9] . 8 2.4 Detail of myosin and actin . 9 2.5 Tension vs length of sarcomere[11] . 10 2.6 Summary of SMA types [17] . 13 2.7 Hysteresis curve in an SMA [16] . 14 2.8 Twinning explanation [16] . 14 2.9 Effect of the bending deformation strain on the TWSME . 15 2.10 Temperature of the TWSME formation . 15 2.11 Moving charge in quartz crystals [20] . 17 2.12 Construction of piezo bimorph actuator [23] . 18 2.13 Piezo bimorph connection methods [24] . 19 2.14 Piezo stroke amplification layouts [25] . 20 2.15 Piezo Walking Actuator steps (Author illustration) . 21 2.16 EAP basic types[27] . 23 2.17 Dielectric EAP function [28] . 23 2.18 Ionic EAP ion flow [30] . 24 3.1 Atomic origins of Magnetics[34] . 27 3.2 Illustration of Domain Walls [34] . 28 3.3 Crystal Structure of Neodymium Iron Borate [38] . 31 ix 3.4 Microelectric Fabrication Steps [49] . 37 4.1 Model of design 1 . 42 4.2 Visualisation of error states, error in orange . 42 4.3 Step illustration of vernier scale principle . 43 4.4 Active Arm Function . 44 4.5 Prototype design solid . 45 4.6 Single-acting through-passing model . 46 4.7 Double-acting Z-disk model . 47 4.8 Bending Arms . 50 4.9 Friction Force Diagram . 51 5.1 Solid design Axonometric view . 56 5.2 Solid design top view . 56 5.3 Solid design head view . 57 5.4 Solid design arm detail . 58 5.5 Solid design shell detail . 58 5.6 Solid design shaft detail . 59 5.7 Revised Shaft and Shell Elements . 62 5.8 Shaft head detail . 63 5.9 Revised Spool element, and section . 63 5.10 Assembly of prototype . 64 5.11 Assembly of prototype spool detail . 64 5.12 End view of assembly . 65 5.13 Rendering of prototype . 66 5.14 Image of produced prototype . ..