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Journal ArticleDOI

Advances in dielectric elastomers for actuators and artificial muscles.

04 Jan 2010-Macromolecular Rapid Communications (Wiley)-Vol. 31, Iss: 1, pp 10-36
TL;DR: A number of materials have been explored for their use as artificial muscles, but dielectric elastomers appear to provide the best combination of properties for true muscle-like actuation, and widespread adoption of DEs has been hindered by premature breakdown and the requirement for high voltages and bulky support frames.
Abstract: A number of materials have been explored for their use as artificial muscles Among these, dielectric elastomers (DEs) appear to provide the best combination of properties for true muscle-like actuation DEs behave as compliant capacitors, expanding in area and shrinking in thickness when a voltage is applied Materials combining very high energy densities, strains, and efficiencies have been known for some time To date, however, the widespread adoption of DEs has been hindered by premature breakdown and the requirement for high voltages and bulky support frames Recent advances seem poised to remove these restrictions and allow for the production of highly reliable, high-performance transducers for artificial muscle applications
Citations
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Journal ArticleDOI
TL;DR: This work describes a composite material composed of a supramolecular organic polymer with embedded nickel nanostructured microparticles, which shows mechanical and electrical self-healing properties at ambient conditions and shows that the material is pressure- and flexion-sensitive, and therefore suitable for electronic skin applications.
Abstract: Pressure sensitivity and mechanical self-healing are two vital functions of the human skin. A flexible and electrically conducting material that can sense mechanical forces and yet be able to self-heal repeatably can be of use in emerging fields such as soft robotics and biomimetic prostheses, but combining all these properties together remains a challenging task. Here, we describe a composite material composed of a supramolecular organic polymer with embedded nickel nanostructured microparticles, which shows mechanical and electrical self-healing properties at ambient conditions. We also show that our material is pressure- and flexion-sensitive, and therefore suitable for electronic skin applications. The electrical conductivity can be tuned by varying the amount of nickel particles and can reach values as high as 40 S cm−1. On rupture, the initial conductivity is repeatably restored with ∼90% efficiency after 15 s healing time, and the mechanical properties are completely restored after ∼10 min. The composite resistance varies inversely with applied flexion and tactile forces. These results demonstrate that natural skin's repeatable self-healing capability can be mimicked in conductive and piezoresistive materials, thus potentially expanding the scope of applications of current electronic skin systems. A supramolecular polymer with embedded nanostructured Ni particles shows mechanical and electrical self-healing capabilities as well as piezoresistive properties, making it a good candidate for electronic skin applications.

1,240 citations

Journal ArticleDOI
TL;DR: A critical overview of soft robotic grippers is presented, covering different material sets, physical principles, and device architectures, and improved materials, processing methods, and sensing play an important role in future research.
Abstract: Advances in soft robotics, materials science, and stretchable electronics have enabled rapid progress in soft grippers. Here, a critical overview of soft robotic grippers is presented, covering different material sets, physical principles, and device architectures. Soft gripping can be categorized into three technologies, enabling grasping by: a) actuation, b) controlled stiffness, and c) controlled adhesion. A comprehensive review of each type is presented. Compared to rigid grippers, end-effectors fabricated from flexible and soft components can often grasp or manipulate a larger variety of objects. Such grippers are an example of morphological computation, where control complexity is greatly reduced by material softness and mechanical compliance. Advanced materials and soft components, in particular silicone elastomers, shape memory materials, and active polymers and gels, are increasingly investigated for the design of lighter, simpler, and more universal grippers, using the inherent functionality of the materials. Embedding stretchable distributed sensors in or on soft grippers greatly enhances the ways in which the grippers interact with objects. Challenges for soft grippers include miniaturization, robustness, speed, integration of sensing, and control. Improved materials, processing methods, and sensing play an important role in future research.

1,028 citations

Journal ArticleDOI
TL;DR: A detailed survey of ongoing methodologies for soft actuators, highlighting approaches suitable for nanometer- to centimeter-scale robotic applications, including both the development of new materials and composites, as well as novel implementations leveraging the unique properties of soft materials.
Abstract: This review comprises a detailed survey of ongoing methodologies for soft actuators, highlighting approaches suitable for nanometer- to centimeter-scale robotic applications. Soft robots present a special design challenge in that their actuation and sensing mechanisms are often highly integrated with the robot body and overall functionality. When less than a centimeter, they belong to an even more special subcategory of robots or devices, in that they often lack on-board power, sensing, computation, and control. Soft, active materials are particularly well suited for this task, with a wide range of stimulants and a number of impressive examples, demonstrating large deformations, high motion complexities, and varied multifunctionality. Recent research includes both the development of new materials and composites, as well as novel implementations leveraging the unique properties of soft materials.

897 citations

Journal ArticleDOI
Zhigang Suo1
TL;DR: In this paper, the authors present a theory of dielectric elastomers, developed within continuum mechanics and thermodynamics, and motivated by molecular pictures and empirical observations, which couples large deformation and electric potential, and describes nonlinear and nonequilibrium behavior, such as electromechanical instability and viscoelasticity.

838 citations

Journal ArticleDOI
TL;DR: In this article, a stretchable polymer LED is fabricated that is capable of emitting light when subjected to strains as large as 120% and a prototype 5 × 5 pixel monochrome display based on an array of these LEDs is demonstrated.
Abstract: A stretchable polymer LED is fabricated that is capable of emitting light when subjected to strains as large as 120%. A prototype 5 × 5 pixel monochrome display based on an array of these LEDs is demonstrated.

826 citations

References
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Journal ArticleDOI
Sumio Iijima1
01 Nov 1991-Nature
TL;DR: Iijima et al. as mentioned in this paper reported the preparation of a new type of finite carbon structure consisting of needle-like tubes, which were produced using an arc-discharge evaporation method similar to that used for fullerene synthesis.
Abstract: THE synthesis of molecular carbon structures in the form of C60 and other fullerenes1 has stimulated intense interest in the structures accessible to graphitic carbon sheets. Here I report the preparation of a new type of finite carbon structure consisting of needle-like tubes. Produced using an arc-discharge evaporation method similar to that used for fullerene synthesis, the needles grow at the negative end of the electrode used for the arc discharge. Electron microscopy reveals that each needle comprises coaxial tubes of graphitic sheets, ranging in number from 2 up to about 50. On each tube the carbon-atom hexagons are arranged in a helical fashion about the needle axis. The helical pitch varies from needle to needle and from tube to tube within a single needle. It appears that this helical structure may aid the growth process. The formation of these needles, ranging from a few to a few tens of nanometres in diameter, suggests that engineering of carbon structures should be possible on scales considerably greater than those relevant to the fullerenes. On 7 November 1991, Sumio Iijima announced in Nature the preparation of nanometre-size, needle-like tubes of carbon — now familiar as 'nanotubes'. Used in microelectronic circuitry and microscopy, and as a tool to test quantum mechanics and model biological systems, nanotubes seem to have unlimited potential.

39,086 citations

Journal ArticleDOI
02 Aug 2002-Science
TL;DR: Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects.
Abstract: Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects. Some of these applications are now realized in products. Others are demonstrated in early to advanced devices, and one, hydrogen storage, is clouded by controversy. Nanotube cost, polydispersity in nanotube type, and limitations in processing and assembly methods are important barriers for some applications of single-walled nanotubes.

9,693 citations

Journal ArticleDOI
04 Feb 2000-Science
TL;DR: It is shown that prestraining the film further improves the performance of electrical actuators made from films of dielectric elastomers coated on both sides with compliant electrode material.
Abstract: Electrical actuators were made from films of dielectric elastomers (such as silicones) coated on both sides with compliant electrode material. When voltage was applied, the resulting electrostatic forces compressed the film in thickness and expanded it in area, producing strains up to 30 to 40%. It is now shown that prestraining the film further improves the performance of these devices. Actuated strains up to 117% were demonstrated with silicone elastomers, and up to 215% with acrylic elastomers using biaxially and uniaxially prestrained films. The strain, pressure, and response time of silicone exceeded those of natural muscle; specific energy densities greatly exceeded those of other field-actuated materials. Because the actuation mechanism is faster than in other high-strain electroactive polymers, this technology may be suitable for diverse applications.

2,969 citations

Journal ArticleDOI
21 May 1999-Science
TL;DR: Predictions based on measurements suggest that actuators using optimized nanotube sheets may eventually provide substantially higher work densities per cycle than any previously known technology.
Abstract: Electromechanical actuators based on sheets of single-walled carbon nanotubes were shown to generate higher stresses than natural muscle and higher strains than high-modulus ferroelectrics. Like natural muscles, the macroscopic actuators are assemblies of billions of individual nanoscale actuators. The actuation mechanism (quantum chemical-based expansion due to electrochemical double-layer charging) does not require ion intercalation, which limits the life and rate of faradaic conducting polymer actuators. Unlike conventional ferroelectric actuators, low operating voltages of a few volts generate large actuator strains. Predictions based on measurements suggest that actuators using optimized nanotube sheets may eventually provide substantially higher work densities per cycle than any previously known technology.

2,334 citations

Book
01 Jan 1991
TL;DR: Ferroelectric tungsten - bronze type niobate crystals as discussed by the authors is a type of ferroelectric crystal material that can be used to construct piezoelectric composites.
Abstract: 1. Introduction - Characteristics of ferroelectrics. 2. Methods for measuring physical properties of ferroelectric materials. 3. Perovskite-type ferroelectrics (Part I). 4. Perovskite-type ferroelectrics (Part II). 5. Lithium niobate and lithium tantalate. 6. Ferroelectric tungsten - bronze type niobate crystals. 7. KDP family, TGS family and other water-soluble ferroelectric crystals. 8. Other ferroelectric crystal materials. 9. Organic ferroelectric materials and piezoelectric composites.

1,516 citations


"Advances in dielectric elastomers f..." refers background in this paper

  • ...Above the Curie temperature a transitionbetweentheparaelectric and ferroelectricphases can be brought about by applying an electric field.([90,91]) The change in phases results in an extremely large change in lattice constant resulting in large bulk strains....

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