Influence of fiber characteristics on directed electroactuation of anisotropic dielectric electroactive polymers with tunability

Subramani, Krishna Bala; Spontak, Richard J.; Ghosh, Tushar K.

doi:10.1016/j.compscitech.2017.11.014

Cited by 17 publications

(9 citation statements)

References 33 publications

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“…As mentioned earlier, one strategy focuses on the fabrication of composite DEs into which aligned fibers are inserted (cf. Figure a), whereas another recent methodology enables anisotropic actuation through the use of oriented carbon nanotubes comprising the compliant electrodes . Complementary materials‐related developments have also been reported, focusing on multilayer designs, bottle‐brush polymers, and high‐permittivity elastomers …”

Section: Resultsmentioning

confidence: 99%

“…In (b), the actuation anisotropy discerned from the ratio of orthogonal strains is presented for OTPEG25, as well as a polymer composite consisting of equibiaxially prestrained VHB‐4905 acrylic elastomer containing aligned, unstrained PU fibers (♦). Maximum anisotropies achieved with other fiber‐modified VHB‐4905 composites (labeled) are included for comparison . The solid lines in (a) and (b) serve as guides for the eye.…”

Section: Resultsmentioning

confidence: 99%

“…For comparison in Figure b, results acquired from a VHB‐4905 DE equibiaxially prestrained to 200% × 200% and modified with unstrained polyurethane (PU) fibers displays actuation anisotropy levels that are generally <2. Also included in Figure b are the highest reported values of composite DEs composed of prestrained VHB‐4905 and containing one of the following fibers: PU (strained to 200%), polyamide (PA), and silicon carbide (SiC). This comparison confirms that the supramolecular approach introduced here to align the semicrystalline crosslinks via mechanical conditioning is on par with or superior to methods intended to achieve anisotropic actuation through the incorporation of aligned fibrous modifiers.…”

Section: Resultsmentioning

confidence: 99%

“…If actuation is restricted to a specific direction, a DE possesses greater capacity for performing mechanical work in that direction. To introduce anisotropic actuation into VHB‐based DEs, several independent efforts have examined polymer composites prepared by incorporating aligned fibers into sandwiched VHB films. By doing so, the tensile moduli parallel and perpendicular to the fiber direction differ substantially, with the modulus along the fiber direction exceeding that normal to the fiber direction.…”

Section: Introductionmentioning

confidence: 99%

“…As a consequence of this difference in mechanical properties, the electromechanical properties exemplified by the orthogonal actuation strains at a constant electric field display similar behavior. Mechanical and actuation anisotropy values can further be discerned from the ratios of these directional mechanical moduli and actuation strains, respectively, and yield actuation‐induced enhancement factors (defined as the ratio of actuation to mechanical anisotropy) that vary with fiber content and, in some cases, extend beyond 250% . Perhaps more importantly is the experimental result that anisotropic actuation serves to improve the electromechanical efficiency, which reflects the conversion from electrical input to mechanical output, by as much as 55% .…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Crystallization‐Directed Anisotropic Electroactuation in Selectively Solvated Olefinic Thermoplastic Elastomers: A Thermal and (Electro)Mechanical Property Study

Armstrong

Spontak

2018

Adv Funct Materials

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Dielectric elastomers (DEs), a class of soft electroactive polymers that change size upon exposure to an external electric field, constitute an increasingly important class of stimuli-responsive polymers due primarily to their large actuation strains, facile and low-cost fabrication, scalability, and mechanical robustness. Unless purposefully constrained, most DEs exhibit isotropic actuation wherein size changes are the same in all actuation directions. Previous studies of DEs containing oriented, stiff fibers have demonstrated, however, that anisotropic actuation along a designated direction is more electromechanically efficient since this design eliminates energy expended in nonessential directions. To identify an alternative, supramolecularlevel route to anisotropic electroactuation, we investigate the thermal and mechanical properties of novel thermoplastic elastomer gels composed of a selectively solvated olefinic block copolymer that not only microphaseseparates but also crystallizes upon cooling from the solution state. While these materials possess remarkable mechanical attributes (e.g., giant strains in excess of 4000%), their ability to be strain-conditioned enables huge anisotropic actuation levels, measured to be greater than 30 from the ratio of orthogonal actuation strains. This work establishes that crystallizationinduced anisotropic actuation can be achieved with these DEs.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201803467.reasons account for this sudden spike in technological interest: (1) development of flexible, stretchable, and otherwise compliant electrode technologies, and (2) discovery of dielectric materials possessing the appropriate electrical and elastomeric properties required to attain large actuation strains. The seminal paper by Pelrine et al. [6] is largely responsible for spurring contemporary DE studies by introducing the use of carbon grease as a compliant electrode in conjunction with a new chemically crosslinked dielectric material, a commercial acrylic adhesive (VHB 4905/4910), that is capable of achieving actuation strains greater than 100% (on an area basis). Since this initial investigation of VHB, the DE community has considered surprisingly few new competitive materials even though VHB remains somewhat proprietary and it is only manufactured in a limited number of thicknesses. Nevertheless, because of its performance, availability and relatively low cost, VHB has dominated the scientific literature as the gold standard to which the performance of other materials is frequently compared. [7][8][9][10] Other examples of chemically crosslinked elastomers that have shown promise as DEs for use in, e.g., (micro)robotics, [11] biomedical devices, [12] and stretchable electronics [13] include silicone elastomers, [14,15] VHB modified [16] with a secondary acrylic network to produce an elastomeric "binetwork," custom-designed acrylic elastomers, [17] and bottlebrush silicone elastomers. [18] An importan...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Crystallization‐Directed Anisotropic Electroactuation in Selectively Solvated Olefinic Thermoplastic Elastomers: A Thermal and (Electro)Mechanical Property Study

Armstrong

Spontak

2018

Adv Funct Materials

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An Anisotropic Dielectric Elastomer Actuator with an Oriented Electrospun Nanofiber Composite Film

Zhang

Chen

Xing

et al. 2023

Adv Materials Technologies

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Anisotropic actuation, a universal phenomenon in nature, may be inspiring for the development of intelligent soft robotics in the future. For dielectric elastomers (DEs), important investigations have been done to decrease the voltage and increase the actuation strain. However, mechanical isotropy of synthetic DEs shows in‐plane uniform deformation, lacking the controllability of the actuation direction. Herein, an anisotropic DE (denoted as ADE) is constructed by casting Ecoflex/BaTiO3 solution onto oriented TPU nanofibrous membranes fabricated via drum electrospinning. The resulting ADE with a seamless three‐layer structure features mechanical anisotropy in the elastic modulus, with the maximum ratio between x and y directions of the plane being 11. A prototype ADE‐based actuator demonstrates a high electroactuation anisotropy of 3.95, a large unidirectional length strain of 15%, and a high energy density of 0.014 MJ m−3 at an electric field of 40 V µm−1. Two potential applications, a flow divider valve simulating the Transwell test in the medical field and a mechanical stimulus component mimicking the maturation of cardiomyocytes, are successfully demonstrated. Thus, this work offers a versatile yet simple approach for fabricating anisotropic electroactive elastomer actuators in the future.

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Review of Dielectric Elastomer Actuators and Their Applications in Soft Robots

Guo

Liu

et al. 2021

Advanced Intelligent Systems

165

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Robots play an increasingly important role in industrial production and daily life. Traditional robots are mostly made of hard materials, such as metal and plastic. Although rigidity of the material enables the traditional robot to perform tasks that are difficult for humans, for instance, carrying heavy objects, it also limits its adaptability. In nature, animals and plants are mostly made of soft materials, which make them have very high compliance and realize a variety of unimaginable actions. Similar to natural creatures, soft robots are usually composed of soft stimuli-responsive materials, which make them have good adaptability and compliance, and can achieve large deformation.Triggered by external stimuli, such as electric fields, magnetic fields, heat, and light, these soft stimuli-responsive materials can deform in a specific direction. The soft stimuli-responsive materials commonly used in soft robots include electroactive polymers (EAP), [1][2][3] hydrogels, [4][5][6][7] magnetic materials, [8][9][10] shape memory polymers (SMP), [11][12][13] shape memory alloys (SMA), [14,15] liquid crystal elastomers (LCE), [16][17][18] and so on. In addition, other actuation methods, such as pneumatic inflation and [19] electrostatic, [20,21] are also widely used in soft robots. To have an overview of different actuation methods, their performances with the maximum values are shown in Table 1. Although these maximum values were obtained from different actuators for each actuation method, they still demonstrate the potential upper limit.Dielectric elastomer (DE) is a typical EAP, which can generate significant deformation under the action of an external electric field. Thanks to its characteristics, such as large deformation, [22,23] fast response, [24,25] low elastic modulus, [2] high energy density, [26,27] light weight, [28,29] and low cost, [28] DE has the reputation of artificial muscles and has become one of the most promising materials in soft robots. [30][31][32][33][34] In this Review, we concentrate on the recent progresses of dielectric elastomer actuators (DEAs) and their application in soft robots. In Section 2, we first introduce the working principle of DEAs, followed by the DE materials and compliant electrodes. Then, various DEAs with different designs are introduced. In Section 3, the application of DEAs in soft robots is divided into seven categories. Some recent highlights are described and discussed in detail, especially those with biological inspiration. We summarize some of the challenges in Section 4 and this is followed with the conclusion in Section 5. Dielectric Elastomer Actuators Working PrincipleGenerally, the structure of a DEA is similar to a sandwich, consisting of a DE membrane, where both surfaces are coated with compliant electrodes, as shown in Figure 1a. Once the compliant electrodes are subjected to voltage, an electric field will be generated in the membrane. The induced Maxwell stress causes the membrane to expand its area and contract its thickness. Based on the mechanism of ...

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Influence of fiber characteristics on directed electroactuation of anisotropic dielectric electroactive polymers with tunability

Cited by 17 publications

References 33 publications

Crystallization‐Directed Anisotropic Electroactuation in Selectively Solvated Olefinic Thermoplastic Elastomers: A Thermal and (Electro)Mechanical Property Study

Crystallization‐Directed Anisotropic Electroactuation in Selectively Solvated Olefinic Thermoplastic Elastomers: A Thermal and (Electro)Mechanical Property Study

An Anisotropic Dielectric Elastomer Actuator with an Oriented Electrospun Nanofiber Composite Film

Review of Dielectric Elastomer Actuators and Their Applications in Soft Robots

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