Carbon-Based Nanomaterials Electrodes of Ionic Soft Actuators: From Initial 1D Structure to 3D Composite Structure for Flexible Intelligent Devices

With the rapid development of autonomous and intelligent devices driven by soft actuators, ion soft actuators in flexible intelligent devices have several advantages over other actuators, including their light weight, low voltage drive, large strain, good flexibility, fast response, etc. Traditional ionic polymer metal composites have received a lot of attention over the past decades, but they suffer from poor driving performance and short service lives since the precious metal electrodes are not only expensive, heavy, and labor-intensive, but also prone to cracking with repeated actuation. As excellent candidates for the electrode materials of ionic soft actuators, carbon-based nanomaterials have received a lot of interest because of their plentiful reserves, low cost, and excellent mechanical, electrical, and electrochemical properties. This research reviewed carbon-based nanomaterial electrodes of ion soft actuators for flexible smart devices from a fresh perspective from 1D to 3D combinations. The design of the electrode structure is introduced after the driving mechanism of ionic soft actuators. The details of ionic soft actuator electrodes made of carbon-based nanomaterials are then provided. Additionally, a summary of applications for flexible intelligent devices is provided. Finally, suggestions for challenges and prospects are made to offer direction and inspiration for further development.

3D Printing of Layered Structures of Metal-Ionic Polymers: Recent Progress, Challenges and Opportunities

Layered Structures of Metal Ionic Polymers, or Ionic Polymer-Metal Composites (IPMCs) are formed by a membrane of an ionic electroactive materials flanked by two metal electrodes on both surfaces; they are devices able to change their shape upon application of an electrical external stimulus. This class of materials is used in various fields such as biomedicine, soft robotics, and sensor technology because of their favorable properties (light weight, biocompatibility, fast response to stimulus and good flexibility). With additive manufacturing, actuators can be customized and tailored to specific applications, allowing for the optimization of performance, size, and weight, thus reducing costs and time of fabrication and enhancing functionality and efficiency in various applications. In this review, we present an overview of the newest trend in using different 3D printing techniques to produce electrically responsive IPMC devices.

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.

Ionomers Based on Addition and Ring Opening Metathesis Polymerized 5-Phenyl-2-norbornene as a Membrane Material for Ionic Actuators

Two types of poly(5-phenyl-2-norbornene) were synthesized via ring opening metathesis and addition polymerization. The polymers sulfonation reaction under homogeneous conditions resulted in ionomer with high sulfonation degree up to 79% (IEC 3.36 meq/g). The prepared ionomer was characterized by DSC, GPC, ¹H NMR and FT-IR. Polymers for electromechanical applications soluble in common polar organic solvents were obtained by replacing proton of sulfonic group with imidazolium and 1-methylimidazlium. Membranes were prepared using the above-mentioned polymers and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4), as well as mixtures with polyvinylidene fluoride (PVDF). Mechanical, morphological, and conductive properties of the membranes were examined by tensile testing, SEM, and impedance spectroscopy, respectively. Dry and air-stable actuators with electrodes based on SWCNT were fabricated via hot-pressing. Actuators with membranes based on methylimidazolium containing ionomers outperformed classical bucky gel actuator and demonstrated high strain (up to 1.14%) and generated stress (up to 1.21 MPa) under low voltage of 2 V.

Recent Advancements in Polyphenylsulfone Membrane Modification Methods for Separation Applications

Polyphenylsulfone (PPSU) membranes are of fundamental importance for many applications such as water treatment, gas separation, energy, electronics, and biomedicine, due to their low cost, controlled crystallinity, chemical, thermal, and mechanical stability. Numerous research studies have shown that modifying surface properties of PPSU membranes influences their stability and functionality. Therefore, the modification of the PPSU membrane surface is a pressing issue for both research and industrial communities. In this review, various surface modification methods and processes along with their mechanisms and performance are considered starting from 2002. There are three main approaches to the modification of PPSU membranes. The first one is bulk modifications, and it includes functional groups inclusion via sulfonation, amination, and chloromethylation. The second is blending with polymer (for instance, blending nanomaterials and biopolymers). Finally, the third one deals with physical and chemical surface modifications. Obviously, each method has its own limitations and advantages that are outlined below. Generally speaking, modified PPSU membranes demonstrate improved physical and chemical properties and enhanced performance. The advancements in PPSU modification have opened the door for the advance of membrane technology and multiple prospective applications.

Sulfonic SiO2 nanocolloid doped perfluorosulfonic acid films with enhanced water uptake and inner channel for IPMC actuators

This study provides a facile and effective strategy to fabricate sulfonic SiO₂ nanocolloid (HSO₃-SiO₂) doped perfluorosulfonic acid (PFSA) films with enhanced water uptake and inner channel for high-performance and cost-effective ionic exchange polymer metal composite (IPMC) actuators. A commercial precursor of mercaptopropyl trimethoxysilane was hydrolyzed to form thiol functionalized SiO₂ nanocolloids (SH-SiO₂, ∼25 nm in diameter), which were further oxidized into sulfonic SiO₂ nanocolloids (HSO₃-SiO₂, ∼14 nm in diameter). Both SiO₂ nanocolloids were used as additives to dope PFSA film for fabricating IPMC-used matrix films. Due to difference of compatibility, the SH-SiO₂ nanocolloids take phase separation in the cocrystallization course, and aggregate into huge, regular spherical particles with a mean diameter of ∼690 μm; while the HSO₃-SiO₂ nanocolloids are completely compatible with PFSA, forming a very homogeneous hybrid matrix film. Related physiochemical investigations by analytical tools revealed that, the resultant HSO₃-SiO₂ hybrid film shows better IPMC-related properties compared to the SH-SiO₂ hybrid film: 1.59 folds in water uptake, and 2.37 folds in ion exchanging capacity, thus contains an increased number of cations and possesses larger and better interconnected inner channels for IPMC bending. Consequently, the HSO₃-SiO₂ hybrid IPMC actuator exhibits remarkably higher levels of actuation behaviours such as higher force output, higher displacement output, and longer stable working time, which could be used as a valuable artificial muscle for flexible actuators or displacement/vibration sensors at low cost.

Data on synthesis and characterization of sulfonated poly(phenylnorbornene) and polymer electrolyte membranes based on it

This article describes data on preparation of sulfonated hydrogenated poly(phenylnorbornene) with different cations synthesized via sequential ring-opening metathesis polymerization, reduction, homogeneous sulfonation and cation exchange reactions. The data of the characterization of new polymers by nuclear magnetic resonance (1H NMR) spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC) are presented. The effect of imidazolium and 1-methylimidazolium cations, ionic liquid and Zwitter-type ion liquid on ionic conductivities evaluated by impedance spectroscopy. Preparation procedure of polymer electrolyte membrane based on new polymers and Nafion as a blend with polyvinylidene fluoride (PVDF) is given. Scanning electron microscopy images and ionic conductivities of these membrane are presented.