Page 282 - Carbon Nanotube Fibres and Yarns

CHAPTER 11

Carbon nanotube yarn-based

actuators

a
Xiaohui Yang , Menghe Miao b
a College of Materials Science and Engineering, Guizhou Minzu University, Guiyang, China
b
CSIRO Manufacturing, Geelong, VIC, Australia
11.1 Introduction

Actuators are material structures or devices that can reversibly contract, ex-
pand, or rotate in one component in response to an external stimulus (such
as pH, current, pressure, temperature, moisture, light, etc.) [1]. An actuator
is usually used to induce a strain into a system in order to generate motion,
change shape, or compensate disturbing vibrations [2]. The functions of
actuators are similar to biological muscles. For many researchers, the term
“flexible actuator” is interchangeable with “artificial muscle.”
The direct conversion of electrical energy and other forms of energy to
mechanical energy through a material response is critically important for
such diverse needs as robotics, optical fiber switches, optical displays, pros-
thetic devices, sonar projectors, and microscopic pumps [3].
Many materials have been investigated for fabricating actuators [4], includ-
ing piezoelectric ceramics [5], shape memory alloys [6], polymers [i.e., shape
memory polymers, conducting polymers (CPs), etc.] [7–10], graphenes [11],
and carbon nanotubes (CNTs) [12]. Among them, CNTs are the most explored
materials owing to their unique structure, high mechanical strength, corrosion
and oxidation resistivity, and electronic and thermal conductivities [13].
CNT-based actuators are made into different forms, for example, sheet
[3, 14–16], film [17], aerogel [18], and yarn [19, 20]. Compared with other
forms, CNT yarns can be twisted, bent, and knotted without structural
failure, and can be further processed into different types of textiles by weav-
ing, knitting, and braiding [21]. CNT yarns-based actuators are designed to
take advantage of the superior flexibility of CNT fibers and yarns, different
energy conversion mechanisms and active materials that can be embedded
in the CNT yarns. Because of their versatility, CNT yarns-based actuators
have shown great potential for a wide range of applications, such as soft
robotics, prosthetics, and smart textiles.

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