Realizing the potential of dielectric elastomer artificial muscles

Soft robotics represents a new set of technologies aimed at operating in natural environments and near the human body. To interact with their environment, soft robots require artificial muscles to actuate movement. These artificial muscles need to be as strong, fast, and robust as their natural counterparts. Dielectric elastomer actuators (DEAs) are promising soft transducers, but typically exhibit low output forces and low energy densities when used without rigid supports. Here, we report a soft composite DEA made of strain-stiffening elastomers and carbon nanotube electrodes, which demonstrates a peak energy density of 19.8 J/kg. The result is close to the upper limit for natural muscle (0.4–40 J/kg), making these DEAs the highest-performance electrically driven soft artificial muscles demonstrated to date. To obtain high forces and displacements, we used low-density, ultrathin carbon nanotube electrodes which can sustain applied electric fields upward of 100 V/μm without suffering from dielectric breakdown. Potential applications include prosthetics, surgical robots, and wearable devices, as well as soft robots capable of locomotion and manipulation in natural or human-centric environments.

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Dielectric Elastomer Actuator for Soft Robotics Applications and Challenges

Applied Sciences ◽

10.3390/app10020640 ◽

2020 ◽

Vol 10 (2) ◽

pp. 640 ◽

Cited By ~ 11

Author(s):

Jung-Hwan Youn ◽

Seung Mo Jeong ◽

Geonwoo Hwang ◽

Hyunwoo Kim ◽

Kyujin Hyeon ◽

...

Keyword(s):

State Of The Art ◽

Dielectric Elastomer ◽

Artificial Muscles ◽

Soft Robot ◽

Optical Components ◽

Dielectric Characteristics ◽

Dielectric Elastomer Actuators ◽

Potential Applications ◽

Working Principle ◽

Soft Actuators

This paper reviews state-of-the-art dielectric elastomer actuators (DEAs) and their future perspectives as soft actuators which have recently been considered as a key power generation component for soft robots. This paper begins with the introduction of the working principle of the dielectric elastomer actuators. Because the operation of DEA includes the physics of both mechanical viscoelastic properties and dielectric characteristics, we describe theoretical modeling methods for the DEA before introducing applications. In addition, the design of artificial muscles based on DEA is also introduced. This paper reviews four popular subjects for the application of DEA: soft robot hand, locomotion robots, wearable devices, and tunable optical components. Other potential applications and challenging issues are described in the conclusion.

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Linear-Quadratic Regulator for Control of Multi-Wall Carbon Nanotube/Polydimethylsiloxane Based Conical Dielectric Elastomer Actuators

Actuators ◽

10.3390/act9010018 ◽

2020 ◽

Vol 9 (1) ◽

pp. 18

Author(s):

Titus Mulembo ◽

Waweru Njeri ◽

Gakuji Nagai ◽

Hirohisa Tamagawa ◽

Keishi Naito ◽

...

Keyword(s):

Carbon Nanotube ◽

Rise Time ◽

Electromechanical Coupling ◽

Linear Quadratic Regulator ◽

Fast Response ◽

Dielectric Elastomer ◽

Soft Robotics ◽

Artificial Muscles ◽

Linear Quadratic ◽

Dielectric Elastomer Actuators

Conventional rigid actuators, such as DC servo motors, face challenges in utilizing them in artificial muscles and soft robotics. Dielectric elastomer actuators (DEAs) overcome all these limitations, as they exhibit complex and fast motions, quietness, lightness, and softness. Recently, there has been much focus on studies of the DEAs material’s non-linearity, the non-linear electromechanical coupling, and viscoelastic behavior of VHB and silicone-based conical DEAs having compliant electrodes that are based on graphite powder and carbon grease. However, the mitigation of overshoot that arises from fast response conical DEAs made with solid electrodes has not received much research focus. In this paper, we fabricated a conical configuration of multi-walled carbon nanotube/polydimethylsiloxane (MWCNT/PDMS) based DEAs with a rise time of 10 ms, and 50% peak overshoot. We developed a full feedback state-based linear-quadratic regulator (LQR) having Luenberger observer to mitigate the DEAs overshoot in both the voltage ON and OFF instances. The cone DEA’s model was identified and a stable and well-fitting transfer function with a fit of 94% was obtained. Optimal parameters Q = 70,000, R = 0.1, and Q = 7000, R = 0.01 resulted in the DEA response having a rise time value of 20 ms with zero overshoot, in both simulations and experiments. The LQR approach can be useful for the control of fast response DEAs and this would expand the potential use of the DEAs as artificial muscles in soft robotics.

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Supramolecular ionic polymer/carbon nanotube composite hydrogels with enhanced electromechanical performance

Nanotechnology Reviews ◽

10.1515/ntrev-2020-0039 ◽

2020 ◽

Vol 9 (1) ◽

pp. 478-488 ◽

Cited By ~ 3

Author(s):

Yun-Fei Zhang ◽

Fei-Peng Du ◽

Ling Chen ◽

Ka-Wai Yeung ◽

Yuqing Dong ◽

...

Keyword(s):

Carbon Nanotube ◽

Ion Mobility ◽

Artificial Muscles ◽

Ionic Polymer ◽

Composite Hydrogels ◽

The Matrix ◽

Electromechanical Performance ◽

Carbon Nanotube Composite ◽

Robotic Devices

AbstractElectroactive hydrogels have received increasing attention due to the possibility of being used in biomimetics, such as for soft robotics and artificial muscles. However, the applications are hindered by the poor mechanical properties and slow response time. To address these issues, in this study, supramolecular ionic polymer–carbon nanotube (SIPC) composite hydrogels were fabricated via in situ free radical polymerization. The polymer matrix consisted of carbon nanotubes (CNTs), styrene sulfonic sodium (SSNa), β-cyclodextrin (β-CD)-grafted acrylamide, and ferrocene (Fc)-grafted acrylamide, with the incorporation of SSNa serving as the ionic source. On applying an external voltage, the ions accumulate on one side of the matrix, leading to localized swelling and bending of the structure. Therefore, a controllable and reversible actuation can be achieved by changing the applied voltage. The tensile strength of the SIPC was improved by over 300%, from 12 to 49 kPa, due to the reinforcement effect of the CNTs and the supramolecular host–guest interactions between the β-CD and Fc moieties. The inclusion of CNTs not only improved the tensile properties but also enhanced the ion mobility, which lead to a faster electromechanical response. The presented electro-responsive composite hydrogel shows a high potential for the development of robotic devices and soft smart components for sensing and actuating applications.

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An Upper Bound of the Bias of Nadaraya-Watson Kernel Regression under Lipschitz Assumptions

Stats ◽

10.3390/stats4010001 ◽

2020 ◽

Vol 4 (1) ◽

pp. 1-17

Author(s):

Samuele Tosatto ◽

Riad Akrour ◽

Jan Peters

Keyword(s):

Upper Bound ◽

Prediction Error ◽

Kernel Estimator ◽

Asymptotic Bias ◽

Surgical Robots ◽

Related Literature ◽

Asymptotic Nature ◽

Potential Applications ◽

Self Driving Cars ◽

Automated Decision Making

The Nadaraya-Watson kernel estimator is among the most popular nonparameteric regression technique thanks to its simplicity. Its asymptotic bias has been studied by Rosenblatt in 1969 and has been reported in several related literature. However, given its asymptotic nature, it gives no access to a hard bound. The increasing popularity of predictive tools for automated decision-making surges the need for hard (non-probabilistic) guarantees. To alleviate this issue, we propose an upper bound of the bias which holds for finite bandwidths using Lipschitz assumptions and mitigating some of the prerequisites of Rosenblatt’s analysis. Our bound has potential applications in fields like surgical robots or self-driving cars, where some hard guarantees on the prediction-error are needed.

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Multi-functional dielectric elastomer artificial muscles for soft and smart machines

Journal of Applied Physics ◽

10.1063/1.4740023 ◽

2012 ◽

Vol 112 (4) ◽

pp. 041101 ◽

Cited By ~ 383

Author(s):

Iain A. Anderson ◽

Todd A. Gisby ◽

Thomas G. McKay ◽

Benjamin M. O’Brien ◽

Emilio P. Calius

Keyword(s):

Dielectric Elastomer ◽

Artificial Muscles ◽

Smart Machines

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Study on non-uniform axial magnetic field induced deformation of soft cylindrical magneto-active actuator

Soft Matter ◽

10.1039/d1sm00757b ◽

2021 ◽

Author(s):

Xiaocheng Hu ◽

Yimou Fu ◽

Tonghao Wu ◽

Shaoxing Qu

Keyword(s):

Magnetic Field ◽

Magnetic Stimulation ◽

Axial Magnetic Field ◽

Soft Robots ◽

Potential Applications

The magneto-active polymers (MAPs) can undergo rapid and noticeable deformation through the external wireless magnetic stimulation, offering a possibility to develop potential applications such as actuators, flexible micro-grippers, soft robots,...

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Highly flexible and transparent dielectric elastomer actuators using silver nanowire and carbon nanotube hybrid electrodes

Soft Matter ◽

10.1039/c7sm01329a ◽

2017 ◽

Vol 13 (37) ◽

pp. 6390-6395 ◽

Cited By ~ 17

Author(s):

Ye Rim Lee ◽

Hyungho Kwon ◽

Do Hoon Lee ◽

Byung Yang Lee

Keyword(s):

Carbon Nanotubes ◽

Carbon Nanotube ◽

Silver Nanowires ◽

Dielectric Elastomer ◽

Silver Nanowire ◽

Dielectric Elastomer Actuator ◽

Dielectric Elastomer Actuators ◽

Transparent Dielectric ◽

Optically Transparent ◽

Highly Stretchable

Electrodes consisting of silver nanowires and carbon nanotubes enable a dielectric elastomer actuator to become highly stretchable and optically transparent.

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Implementation of Soft-Lithography Techniques for Fabrication of Bio-Inspired Multi-Layer Dielectric Elastomer Actuators with Interdigitated Mechanically Compliant Electrodes

Actuators ◽

10.3390/act7040073 ◽

2018 ◽

Vol 7 (4) ◽

pp. 73 ◽

Cited By ~ 3

Author(s):

Mert Corbaci ◽

Wayne Walter ◽

Kathleen Lamkin-Kennard

Keyword(s):

Soft Lithography ◽

Skeletal Muscles ◽

Actuation Voltage ◽

Transition Process ◽

Humanoid Robots ◽

Dielectric Elastomer ◽

Industrial Robots ◽

Artificial Muscles ◽

Dielectric Elastomer Actuators ◽

Soft Actuators

Advancements in software engineering have enabled the robotics industry to transition from the use of giant industrial robots to more friendly humanoid robots. Soft robotics is one of the key elements needed to advance the transition process by providing a safer way for robots to interact with the environment. Electroactive polymers (EAPs) are one of the best candidate materials for the next generation of soft robotic actuators and artificial muscles. Lightweight dielectric elastomer actuators (DEAs) provide optimal properties such as high elasticity, rapid response rates, mechanical robustness and compliance. However, for DEAs to become widely used as artificial muscles or soft actuators, there are current limitations, such as high actuation voltage requirements, control of actuation direction, and scaling, that need to be addressed. The authors’ approach to overcome the drawbacks of conventional DEAs is inspired by the natural skeletal muscles. Instead of fabricating a large DEA device, smaller sub-units can be fabricated and bundled together to form larger actuators, similar to the way myofibrils form myocytes in skeletal muscles. The current study presents a novel fabrication approach, utilizing soft lithography and other microfabrication techniques, to allow fabrication of multilayer stacked DEA structures, composed of hundreds of micro-sized DEA units.

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A STUDY OF THE ELECTRICAL PROPERTIES OF Al2O3 FILMS DEPOSITED ON GaAs SUBSTRATES BY SPRAY PYROLYSIS

Surface Review and Letters ◽

10.1142/s0218625x02004128 ◽

2002 ◽

Vol 09 (05n06) ◽

pp. 1637-1640 ◽

Cited By ~ 3

Author(s):

J. CHAVEZ-RAMIREZ ◽

M. AGUILAR-FRUTIS ◽

M. GARCIA ◽

E. MARTINEZ ◽

O. ALVAREZ-FREGOSO ◽

...

Keyword(s):

Aluminum Oxide ◽

Spray Pyrolysis ◽

Electric Fields ◽

Dielectric Breakdown ◽

Spray Pyrolysis Technique ◽

Interface State ◽

State Density ◽

Oxide Semiconductor ◽

Electrical Characteristics ◽

Gaas Substrates

Electrical characteristics of high quality aluminum oxide thin films deposited by the spray pyrolysis technique on GaAs substrates are reported. The films were deposited using a spraying solution of aluminum acetylacetonate in N,N-dimethylformamide and an ultrasonic mist generator. The substrates were (100) GaAs wafers Si-doped (1018 cm -3). The substrate temperature during deposition was in the range of 300–600°C. The electrical characteristics of these films were determined by capacitance and current versus voltage measurements by the incorporation of these films into metal-oxide-semiconductor structures. The interface state density resulted in the order of 1012 1/ eV-cm 2 and the films can stand electric fields higher than 5 MV/cm, without observing a destructive dielectric breakdown. The refractive index, measured by ellipsometry at 633 nm, resulted close to 1.64. The determination of the chemical composition of the films was achieved by energy dispersive X-ray spectroscopy; it resulted close to that of stoichiometric aluminum oxide (O/Al = 1.5) when films are deposited at substrate temperatures of 300–350°C.

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Novel Behavior in Smart Polymeric Materials: Stress Memory and its Potential Applications

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.97.93 ◽

2016 ◽

Vol 97 ◽

pp. 93-99

Author(s):

Jin Lian Hu ◽

Harishkumar Narayana

Keyword(s):

Magnetic Field ◽

Shape Memory ◽

Smart Materials ◽

Shape Memory Polymers ◽

Polymeric Materials ◽

External Stimulus ◽

Artificial Muscles ◽

Recovery Stress ◽

Stress Memory ◽

Potential Applications

Materials, structures and systems, responsive to an external stimulus are smart and adaptive to our human demands. Among smart materials, polymers with shape memory effect are at the forefront of research leading to comprehensive publications and wide applications. In this paper, we extend the concept of shape memory polymers to stress memory ones, which have been discovered recently. Like shape memory, stress memory represents a phenomenon where the stress in a polymer can be programmed, stored and retrieved reversibly with an external stimulus such as temperature and magnetic field. Stress memory may be mistaken as the recovery stress which was studied quite broadly. Our further investigation also reveals that stress memory is quite different from recovery stress containing multi-components including elastic and viscoelastic forces in addition to possible memory stress. Stress memory could be used into applications such as sensors, pressure garments, massage devices, electronic skins and artificial muscles. The current revelation of stress memory potentials is emanated from an authentic application of memory fibres, films, and foams in the smart compression devices for the management of chronic and therapeutic disorders.

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