The performance of Nafion-based IPMC actuators containing polypyrrole/alumina composite fillers

Recent Progress in Development and Applications of Ionic Polymer-Metal Composite

Electroactive polymer (EAP) is a polymer that reacts to electrical stimuli, such as voltage, and can be divided into electronic and ionic EAP by an electrical energy transfer mechanism within the polymer. The mechanism of ionic EAP is the movement of the positive ions inducing voltage change in the polymer membrane. Among the ionic EAPs, an ionic polymer-metal composite (IPMC) is composed of a metal electrode on the surface of the polymer membrane. A common material for the polymer membrane of IPMC is Nafion containing hydrogen ions, and platinum, gold, and silver are commonly used for the electrode. As a result, IPMC has advantages, such as low voltage requirements, large bending displacement, and bidirectional actuation. Manufacturing of IPMC is composed of preparing the polymer membrane and plating electrode. Preparation methods for the membrane include solution casting, hot pressing, and 3D printing. Meanwhile, electrode formation methods include electroless plating, electroplating, direct assembly process, and sputtering deposition. The manufactured IPMC is widely demonstrated in applications such as grippers, micro-pumps, biomedical, biomimetics, bending sensors, flow sensors, energy harvesters, biosensors, and humidity sensors. This paper will review the overall field of IPMC by demonstrating the categorization, principle, materials, and manufacturing method of IPMC and its applications.

Dendrite Growth and Performance of Self-Healing Composite Electrode IPMC Driven by Cu2

As a kind of flexible intelligent driving material, ionic polymer-metal composite (IPMC) has attracted the attention of researchers due to its advantages of lightweight, large deformation, and fast response. However, the reciprocating bending of IPMC causes cracks to appear on the surface metal electrode layer and reduces the water uptake (WUP). At the same time, the metal particles are extruded, resulting in an increase in resistivity, which affects the driving performance of the materials. Therefore, in this study, considering the preparation cost, Cu-Pt-IPMC using Pt and Cu as a composite electrode with the self-healing system was prepared by electroless plating and Cu²⁺ was used as driving ions that can form a reversible circulation system with a copper electrode. The WUP, surface resistivity, and driving performance were tested and analyzed and the surface roughness was characterized by Matlab. The results show that the dendritic interface electrodes (DIEs) appear at the contact interface between the metal electrode and the film, which extend deeper and wider in the film with the increase in the cycles of autocatalytic platinum plating (ACP-Pt), and the output displacement and blocking force of 61.20 mm and 34.26 mN, respectively, have been achieved in the Cu-Pt-IPMC sample after three cycles of ACP-Pt. Based on these analyses, this study proves that the presence of Cu²⁺ can repair the cracked electrode on the surface of IPMC and reduce the surface electrode resistance, improving the driving performance.

Newton Output Blocking Force under Low-Voltage Stimulation for Carbon Nanotube-Electroactive Polymer Composite Artificial Muscles

This is a study on the development of carbon nanotube-based composite actuators using a new ionic liquid-doped electroactive ionic polymer. For scalable production purposes, a simple hot-pressing method was used. Carbon nanotube/ionic liquid-Nafion/carbon nanotube composite films were fabricated that exhibited a large output blocking force and a stable cycling life with low alternating voltage stimuli in air. Of particular interest and importance, a blocking force of 1.5 N was achieved at an applied voltage of 6 V. Operational durability was confirmed by testing in air for over 30 000 cycles (or 43 h). The superior actuation performance of the carbon nanotube/ionic liquid-Nafion/carbon nanotube composite, coupled with easy manufacturability, low driving voltage, and reliable operation, promises great potential for artificial muscle and biomimetic applications.

Electrochemical and electromechanical behavior of Nafion-based soft actuators with PPy/CB/MWCNT nanocomposite electrodes

In this work, as an alternative to precious platinum electrodes in IPMC actuators, PPy/CB/MWCNT electrode actuators were successfully fabricated by electropolymerization of PPy on both sides of the CB/MWCNT-coated Nafion membranes.

Ionic polymer-metal composite actuators based on triple-layered polyelectrolytes composed of individually functionalized layers

Ionic polymer-metal composite (IPMC) actuators based on two types of triple-layered Nafion composite membranes were prepared via consecutive solution recasting and electroless plating methods. The triple-layered membranes are composed of a Nafion layer containing an amphiphilic organic molecule (10-camphorsulfonic acid; CSA) in the middle section (for fast and large ion conduction) and two Nafion/modified inorganic composite layers in the outer sections (for large accumulation/retention of mobile ions). For construction of the two types of IPMCs, sulfonated montmorillonite (MMT) and polypyrrole (PPy)-coated alumina fillers were incorporated into the outer layers. Both the triple-layered IPMCs exhibited 42% higher tip displacements at the maximum deflections with a negligible back-relaxation, 50-74% higher blocking forces, and more rapid responses under 3 V dc, compared with conventional single-layered Nafion-IPMCs. Improvements in cyclic displacement under a rectangular voltage input of 3 V at 1 Hz were also made in the triple-layered configurations. Compared with single-layered IPMCs consisting of the identical compositions with the respective outer composite layers, the bending rates and energy efficiencies of both the triple-layered IPMCs were significantly higher, although the blocking forces were a bit lower. These remarkable improvements were attributed to higher capacitances and Young's moduli as well as a more efficient transport of mobile ions and water through the middle layer (Nafion/CSA) and a larger accumulation/retention of the mobile species in the outer functionalized inorganic composite layers. Especially, the triple-layered IPMC with the PPy-modified alumina registered the best actuation performance among all the samples, including a viable actuation even at a low voltage of 1.5 V due to involving efficient redox reactions of PPy with the aid of hygroscopic alumina.

Effects of the Polypyrrole/Silica on the Output Force of Ionic Polymer-Metal Composite

In this paper, a polypyrrole (PPy)/SiO2 composite filler prepared via in situ polymerization of pyrrole (Py) on SiO2 particles was incorporated into Nafion to improve the performance of ionic polymer-metal composite (IPMC) actuators. A transmission electron microscope (TEM) was used to observe the morphology of the prepared PPy/SiO2. IPMC with 1% and 2% PPy/SiO2 was synthesized, and the elastic modulus, the electric current, the blocking force and the water retention ability were measured on the test apparatus. Results showed that IPMC with 1% PPy/SiO2 composite, synthesized with 0.5ml Py, exhibited the best mechanical property. Compared with the pure Nafion-IPMC, the blocking force of PPy/SiO2/Nafion-IPMC with the optimized filler content (34.68 mN) at the sinusoidal voltage of 3 V and 0.1Hz was 2.3 times higher. Such significantly improved performance was attributed to the PPy’s redox reaction, which facilitates the ion transport in IPMC. Furthermore, the reasonable amount of the PPy and PPy/SiO2 plays an important role in fabricating the homogeneously distributed PPy/SiO2/Nafion membrane.