Degree Name

Doctor of Philosophy


School of Mechanical, Materials and Mechatronic Engineering


Actuators are devices that exhibit reversible change in their shape or volume or generate force when externally stimulated. Because of their very similar operation style to biological muscles, actuator materials are also known as artificial muscles. These materials are in demand for many applications, such as medical devices and robotics. These applications normally require an inexpensive actuator system that can offer high force, high strain, and high power density in a relatively short period of time. The device packaging and size of the actuator are also important parameters as currently most of the applications desire very compact and lightweight systems. Furthermore, low electricity consumption also as a last requirement has a significant effect on the actuation system by increasing the efficiency of the entire system. Producing all of the above requirements in one device is currently a challenge for engineers and scientists.

In this thesis, a new contractile artificial muscle system is introduced than can offer most of the above requirements to satisfy the current expectations of these devices. Chapter 1 of this thesis focuses on a literature review of prominent available artificial muscles and comparing them with biological muscle performance for better understanding of their advantages and disadvantages. Chapter 2 investigates the effect of the inner tube material and muscle geometry on a small hydraulic McKibben artificial muscle as well as the possibility of running this system with a compact, low voltage water pump. This chapter also introduces a new equation that is able to predict static muscle performance notably more accurately than previous models. Chapter 3 illuminates the possibility of three-dimensional printing the braided sleeve used in McKibben artificial muscles to have more control on the manufacturing process of such devices. In Chapter 4, the fluid normally used in conventional McKibben muscles is substituted with a temperature sensitive material to eliminate the need of the pump/compressor and piping to introduce a more compact device. The new muscles were stimulated either by immersing in a hot water bath or using a heating filament. A contraction strain of 9 % and 2 N isometric force were produced. A new equation is also introduced to predict the performance of this type of McKibben muscles with temperature as the driving force. Chapter 5 introduces a novel miniature type of McKibben artificial muscle by using a conductive braided sleeve and eliminating the need for the inner tube. The electricity consumption of this muscle is as low as 2.5 V. The muscle weight is only 0.14 gr with a diameter of 1.4 mm. The muscle generates a tensile stress of 50 kPa and contraction strain of 10%. Finally, Chapter 6 concludes this study and also represents some potential future works.



Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.