Effect of Ionic Polymer Membrane with Multiwalled Carbon Nanotubes on the Mechanical Performance of Ionic Electroactive Polymer Actuators

Abstract

Ionic electroactive polymer (IEAP) actuators have received interest because of their advantageous properties, including their large displacement, high energy density, light weight, and low power consumption under a low electric field. However, they have a low blocking force under driving, and it is difficult to control the thickness of the ionic polymer membrane. In this study, an IEAP actuator is fabricated using a Nafion membrane with added multiwalled carbon nanotubes to increase the blocking force. A heat press two-step process is also developed to produce a constant and uniform membrane. The fabricated Nafion membrane with 0.2 wt% multiwalled carbon nanotubes has the largest displacement and highest blocking force. As a result, the developed heat press two-step method can be used in various polymer-casting fields, and the fabricated carbon nanotube-based IEAP actuators can serve as useful references in fields such as flexible robotics and artificial muscles.Polymers 2020, 12, 396 2 of 10 membrane with a controlled thickness. So, after the casting process, a new method of controlling the thickness through additional processes was needed. The heat press is good because it can process heat and pressure at the same time, but the fine and constant thickness control method needs to be further investigated. Therefore, the process using the metal plate and the heat press was further performed after the casting to obtain a uniform membrane having a controlled thickness.Moreover, IEAP actuators have significant drawbacks such as low actuation bandwidth, low blocking force, and poor durability [21][22][23][24]. Their low blocking force has particularly hindered the practical applicability of IEAP actuators, necessitating studies on increasing their blocking force. The thicker membrane layer or the thicker electrode layer can cause a displacement decrease of the actuator [8][9][10], and the stiffer electrode layer can cause cracks on the electrode surface, and poor durability of the actuator in operation. Therefore, the application of various materials such as graphene, fullerene, carbon-metals, and graphene oxide to the actuator is studied to increase blocking force or improve actuation performances without reducing displacement [11][12][13][14][15][16][25][26][27][28]. Among various proposed additive materials, multiwalled carbon nanotubes (MWCNTs) have shown high chemical and thermal stability, excellent tensile strength and stiffness, and high conductivity and heat resistance. The excellent properties of the MWCNTs improve the mechanical, electrical, and thermal properties of various polymers [29][30][31][32]. The MWCNT was used to increase the blocking force while maintaining the displacement. However, acid treatments are commonly required in the dispersing process; these treatments damage actuators and affect their mechanical properties owing to the resulting CNT structural defects, which are undesirable for further actuator applications [33]. In contrast, Nafion can be used as an alternative to acid treatment to ...

Review on Improvement, Modeling, and Application of Ionic Polymer Metal Composite Artificial Muscle

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“…Upon activation, ionic EAPs can be used to produce bending phenomena due to their specific ion movements in an electrical field 27,36,[44][45][46][47][48] . Several types of ionic EAPs have been developed, such as ionic polymer gels [48][49][50][51][52] , ionic polymer-metal composites (IPMCs) 40,41,[53][54][55][56][57][58][59][60][61][62] , nanocarbon EAPs 30,[63][64][65][66][67][68][69] and conductive polymer EAPs 28,70 . Their flexible nature and bending mechanism garner much interest in the development of artificial muscles, soft robots and flexible/wearable sensors 29,47,53,71 .…”

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