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State-of-the-Art and Perspectives for Electroactive Polymers
Published in Inamuddin, Mohd Imran Ahamed, Rajender Boddula, Adil A. Gobouri, Electroactive Polymeric Materials, 2022
Rita Martins, Parastou Sadeghi, Ana P.M. Tavares, Goreti Sales
Ionic polymer–metal composite (IPMC) materials consist of an ionomeric membrane ≤100 µm thick that have a thin layer of a noble metal electrode (i.e., platinum) coating it (Pugal et al., 2010; Baglio and Bulsara, 2006; Kim and Tadokoro, 2007; MohdIsa, Hunt, and HosseinNia, 2019). Similar to ionic gels, IPMCs contain an ionic group covalently bonded at the polymer chain (Unal et al., 2019; Park et al., 2008). The membrane usually contains as the ionic group a sulfonic acid (–SO3-) or a carboxylic acid (–COO-), which is aimed at cation exchange. The most used polymer for IPMC is perfluorinated, with sulfonated (NafionTM) and carboxylated (FlemionTM) moieties (Unal et al., 2019; Tiwari and Garcia, 2011; Park et al., 2008). Its electromechanical actuation accounts for the electrostatic interaction between the ionic groups and water molecules, and therefore, creates a pathway for the migration of ions. Under an applied voltage (usually 2–7 V), the ions and water molecules move within the polymer and cause a shape change in the IPMC (Figure 1.4) (Kim and Tadokoro, 2007; MohdIsa, Hunt, and HosseinNia, 2019; Bar-Cohen et al., 2002; Yang et al., 2019).
Current Trends for Actuators and Micromechatronics
Published in Kenji Uchino, Micro Mechatronics, 2019
Elastically soft actuators (i.e., artificial muscle) are composed of polymer materials, because large strains can be generated in polymer materials without causing mechanical damage because of their high elastic compliance. So-called electroactive polymers (EAPs) can be classified as in Table 1.2. The principle of ionic polymer metal composite (IPMC) can be explained as follows in a case of Pt-electroded Nafion film: cations and solvent migrate toward the cathode, resulting in a bending toward the anode side (the bending occurs during changes in potential). An AC field can be used to cause the membrane to bend from site to site with up to 50 Hz. Conducting polymers with conjugated polymers can also be used as actuators. A composite structure results when pyrrole is electropolymerized in the presence of a bulky anion like sodium dodecyl-benzene-sulphonate (DBS). In the as-prepared (oxidized) form, the polypyrrole (PPy) is positively charged and electronically conducting. The charges are balanced by DBS counter ions. When the material is reduced, PPy chains are neutralized, and cations and solvent molecules are dragged into the structure in order to compensate for the charges of the DBS. In other words, an electrically activated swelling of the material results.8 Since “ionic”-type actuators are slow in response (lower than 50 Hz) and environmentally sensitive (e.g., humidity), we will not detail them further in this textbook.
Polymers in Special Uses
Published in Manas Chanda, Plastics Technology Handbook, 2017
Ionic polymer–metal composites (IPMCs) consist of a solvent-swollen ion-exchange polymer mem-brane laminated between two thin flexible metal (typically, percolated Pt nanoparticles or Au) or carbon-based electrodes [59]. Application of a bias voltage to the device causes the migration of mobile ions within the film to the oppositely charged electrode and the concomitant migration of solvent causes the ion-rich region to swell, generating a bending motion. Over time, the actuator will relax slightly because of the built-up pressure gradient. A schematic representation of the actuation mechanism is shown in Figure 5.28. Typical bending materials include Nafion and Flemion with anionic side groups or polystyrene ionomers with anionic-substituted phenyl rings. IPMCs based on a sulfonated poly(styrene-b-ethylene-co-butylene-b-styrene) ionic membrane have been shown [60] to be capable of high-speed bending actuation under constant voltages and excellent harmonic responses under sinusoidal excitation. Driving voltages are typically on the order of a few volts or less and actuation strains and stresses of >3% and 30 MPa, respectively, have been reported. IPMCs have been shown to be well suited for use as soft actuators for bending and sensing [61]. Potential applications include mechanical grippers, metering valves, micropumps, and sensors [59,62]. Eamex (Japan) has developed a commercially available fish robot that uses IPMC actuators.
Deformation mechanism of hydrogen-assisted ionic polymer metal composite actuator
Published in Mechanics of Advanced Materials and Structures, 2023
Ionic polymer metal composite (IPMC) actuators are soft actuators composed of an ionic conductive polymer coated with electrodes [1–6]. These actuators are characterized by attractive features such as relatively low voltage requirement, light weight, flexibility, and easy miniaturization. The driving mechanism of an IPMC actuator is based on the movement of hydrated cations inside the electrolyte polymer membrane. When an electric field is applied, hydrated cations move to the cathode side, increasing the volume of the cathode side membrane [7–9]. Because the polymer membrane is soft and flexible, IPMC actuators exhibit a large bending motion and can be considered as promising candidates for use as micro-actuators in small robots, microvalves, or artificial muscles [10–18].
Printing ionic polymer metal composite actuators by fused deposition modeling technology
Published in International Journal of Smart and Nano Materials, 2021
Guoxiao Yin, Qingsong He, Xiangman Zhou, Yuwei Wu, Hongkai Li, Min Yu
Ionic polymer–metal composites (IPMCs), one kind of ionic electroactive polymers, have the advantages of low driving voltage (usually 1~5 V), large deformation, light weight, no noise, high flexibility, and good biocompatibility [1–5]. The intermediate layer of IPMCs is ion–exchange resin (typically perfluorosulfonic acid cation exchange Nafion membrane), while the two side layers of IPMCs are noble metal electrodes (such as platinum and gold) formed by electroless plating [6]. When voltage is applied on both sides of IPMCs, the hydrated cations inside IPMCs migrate to the cathode under the action of electric field, causing the difference in ionic concentration on both sides of the membrane. This difference results in an expanded cathode and a contracted anode, showing a bending phenomenon [7,8], and IPMCs can produce reciprocating oscillation under alternating current (AC) input. In addition, using electrostatic power to drive IPMCs is also a possible approach [9]. But the voltage of the nanogenerator is high and the current and power are small [10]. In order to drive the IPMCs, the nanogenerator must have a voltage of 1~10 V and power of several watts [11–13]. IPMCs are widely used in medical and bionic robot fields, including medical catheters [11,14–16], surgical microforceps [12], heart-compression devices [17], underwater robots and biomimetic fish [18,19], driving of imitation gecko toes [20], and flapping devices of bionic insects [13]. IPMCs are traditionally fabricated by electroless plating based on the commercial recast membrane, which has some shortcomings such as a long fabrication period, a tedious process, a single shape and an uncontrollable thickness. So the commercial recasted membrane greatly limits the application and development of IPMC. Therefore, multitudinous scholars have searched for new methods to fabricate IPMCs. For example, Park et al. [21], Bonomo et al. [22], Tiwari et al. [23], and Lee et al. [24] extruded Nafion particles or multiple Nafion membranes into thicker Nafion membranes by hot-pressing method, but this method requires making molds in advance and the production process is tedious. Trabia et al. prepared a Nafion membrane by spraying, requiring a relative mold in advance, but this process takes a long time to form Nafion membrane and also causes serious swellings [25]. Malone et al. prepared IPMCs using a mixture of Nafion solution, alcohol, and water as the intermediate layer and a mixture of silver particles and Nafion solution as the electrode material. However, this method has difficulty in controlling the shape of the molding and the specimen has poor surface quality and deformation performance [26]. Luo et al. achieved the printing of electrode layer with single-wall carbon nanotubes and Nafion-intermediate layer by means of direct writing technology, but the specimen prepared by this method is partially fractured [27].