design, fabrication, and characterization of soft pneumatic actuators towards soft wearable robotic

217 Pages·2017·8 MB·English

by  Yap Hong Kai

DESIGN, FABRICATION, AND CHARACTERIZATION OF
SOFT PNEUMATIC ACTUATORS TOWARDS SOFT
WEARABLE ROBOTIC APPLICATIONS

YAP HONG KAI
(B.Eng. (Hons.), NUS)

A THESIS SUBMITTED
FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
NUS GRADUATE SCHOOL FOR INTEGRATIVE
SCIENCES AND ENGINEERING
NATIONAL UNIVERSITY OF SINGAPORE

2017

Supervisor:
Assistant Professor Raye Yeow Chen Hua

Examiners:
Associate Professor Yu Haoyong
Assistant Professor Zhu Jian
Associate Professor Derek Kamper, North Carolina State
University

Declaration

I hereby declare that the thesis is my original work and it has
been written by me in its entirety. I have duly acknowledged all
the sources of information which have been used in the thesis

This thesis has also not been submitted for any degree in any
university previously.

_________________
Yap Hong Kai
3 August 2017

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Acknowledgements
I would like to acknowledge the contributions of the following
individuals, without whom my PhD dissertation could not have come to
fulfillment.
First of all, I would like to express my sincerest gratitude to Dr. Raye
Yeow Chen Hua for giving me the opportunity to pursue research in the
Evolution Innovation Lab. His guidance and helpful pointers have shaped the
way my research has evolved over the past four years. I was given tremendous
freedom and unlimited resources to explore the research questions and
challenges. Additionally, I am indebted to him for the opportunities he laid out
during my PhD journey, from introducing me to other professionals, helping me
to build a network in this field, and allowing me to attend many conferences
and exhibitions to showcase my research.
Second, I would like to thank my outstanding thesis advisory committee
members, Associate Professor Ong Soh Khim and Associate Professor Yu
Haoyong. During the course of my research, they have provided me with critical
advice and endless support which has shaped my thinking. I am indebted to
them for their constant support developing my independent research abilities
through sharing their personal experience. I am also grateful to Dr Lim Jeong
Hoon for his mentorship and supervision of my clinical studies despite his heavy
clinical workload. He has provided me with great resources and the opportunity
to work with patients. Additionally, I have been fortunate to work on several
collaborative projects with Dr Fatima Nasrallah, Professor Lim Chwee Teck,
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Joo Chuan, and Nazir. They have demonstrated to me that a fruitful research
always comes from collaboration among different experts.
My graduate student life is extremely memorable thanks to this special
group of people in the lab, Sunyi, Xinquan, May, Sharmila, Nicholas, Tiana,
Rainier, Chai, Luis, Gokula, Fanzhe, Chan, Jinhuat, Kokkeong and many more.
From engaging discussions of research to small talk and gossip, they have
provided me a warm and friendly working environment. A big thank you to my
previous students, Benjamin, Huiyong, Tzehui, Kang Loong, Aaron, David,
Fred, Chris, and Andrew, who have also contributed to this research. Special
thanks also go out to Bipin, Jane, Dor Ngi, Prof Neo for their supports and many
good chats on entrepreneurship and innovation.
I am also grateful to the friendly staff from Department of Biomedical
Engineering and NUS Graduate School of Integrative Sciences and Engineering
(NGS), especially Irene, Joan, Rahiem, and Kun Song for their support with any
administrative matters. I could not have achieved anything without the generous
financial support from NGS scholarship, which provided me with a stipend and
facilitated my travels to many international conferences to meet other great
minds.
Lastly and most importantly, I would like to thank to the people close to
my heart: my family. To my mum and dad, you have given me all you have. I
would not be where I am today without your unconditional love and care. You
are my constant motivation to achieve what I want to achieve in my life. To my
siblings, Jing Xuan and Hong Siang, thank you for your support and all the fun
and laughter. Let us continue to work hard and make our parents proud. Finally,
to Sheng Yi, thank you for always being there, encouraging me to pursue my
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dreams and keeping me strong during both good and tough times. Here’s to
many more adventures together in the future. I dedicate my thesis to all of you
and I love you all.
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Contents

Summary ..................................................................................... viii
List of Publications ........................................................................ x
List of Tables ............................................................................... xvi
List of Figures ............................................................................ xvii

Chapter 1: Introduction ................................................................ 1
1.1 Motivation 1
1.2 Literature Review 2
1.3 Challenges 13
1.4 Rationale and Original Contributions 14

Chapter 2: Design and Characterization of Soft Elastomeric
Actuators for Hand Assistive Applications ............................... 17
2.1 Preface 18
2.2 Introduction 18
2.3 Design and Characterization of Soft Elastomeric Actuators 21
2.4 Wearable Hand Assistive Exoskeleton with Soft Elastomeric Actuators 35
2.5 Discussion and Conclusion 53
2.6 Supplementary Materials 59

Chapter 3: Kinematic Detection of Soft Elastomeric Actuators
via Integrated Strain Sensors ..................................................... 67
3.1 Preface 68
3.2 Introduction 69
3.3 Soft Actuators with Integrated Resistive Strain Sensors 70
3.4 Wearable Hand Exoskeleton with Integrated Resistive Strain Sensors 87
3.5 Soft Actuators with Fiber Bragg Grating-based Strain Sensors 90
3.6 Wearable Hand Exoskeleton with Fiber Bragg Grating-based Strain Sensors 94
3.7 Discussion and Conclusion 109

Chapter 4: High Force Printable Pneumatic Actuators for Soft
Robotic Applications ................................................................. 112
4.1 Preface 113
4.2 Introduction 113
4.3 Design and Fabrication of Printable Soft Pneumatic Actuators 114
4.4 Modeling of Printable Soft Pneumatic Actuators 125
4.5 Characterization of Printable Soft Pneumatic Actuators 129
4.6 Wearable Hand and Wrist Exoskeleton with Printable Pneumatic Actuators 140
4.7 Discussion and Conclusion 141
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Chapter 5: Fully Fabric-Based Bi-directional Actuators for
Hand Assistive Applications ..................................................... 143
5.1 Preface 144
5.2 Introduction 144
5.3 Design and Fabrication of Fabric-based Pneumatic Actuators 147
5.4 Characterization of Fabric-based Pneumatic Actuators 149
5.5 Wearable Hand Exoskeleton with Fabric-based Pneumatic Actuators 155
5.6 Discussion and Conclusion 160
5.7 Supplementary Materials 164

Chapter 6 Conclusions and Future Work ............................... 171
6.1 Summary of Contributions 171
6.2 Future Work 177

Bibliography ............................................................................... 180

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Summary

Over the past decade, soft robotics has gained a lot of research and
commercial interest and shown potential in a range of applications including
wearable robotics. This dissertation aims to explore the feasibility of utilizing
soft robotic technology for wearable robotic applications. In the field of soft
robotics, soft pneumatic actuators are of particular interest due to their inherent
compliance and reduced control complexity. The objective of this dissertation
is to develop soft pneumatic actuators that are suitable for wearable robotic
applications, particularly on hand assistive exoskeletons.
To accomplish this goal, we have developed soft pneumatic actuators
using different types of materials and fabrication techniques. We proposed
multiple designs of soft pneumatic actuators made from silicone elastomer, 3D
printing filaments and thermoplastic urethane-coated fabrics using different
fabrication techniques, including molding, fused deposition modeling and
ultrasonic welding. The actuators were characterized systematically in terms of
their bending radius of curvature, force output, durability and operating
pressures. This dissertation provides a systematic comparison and design
guideline for soft pneumatic actuators with different actuation mechanisms. To
our best knowledge, we have proposed the first-in-class approach to directly 3D
print airtight soft pneumatic actuators using fused deposition modeling
technology and to fabricate fully fabric-based soft pneumatic actuators using
ultrasonic welding. We further investigated the feasibility of using these
actuators to develop wearable hand exoskeletons for assistive and rehabilitation
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