Dielectric Elastomer Grippers

This paper appraisals state-of-the-art dielectric elastomer actuators (DEAs) and their forthcoming standpoints as soft actuators which have freshly been considered as a crucial power generation module for soft robots. DEs behave as yielding capacitors, expanding in area and attenuation in thickness when a voltage is applied. The paper initiates with the explanation of working principle of dielectric elastomer grippers. Here the operation of DEAs include both physics and mechanical properties with its characteristics, we have describe methods for modelling and its introductory application. In inclusion, the artificial muscle based on DEA concept is also formally presented. This paper also elaborates DEAs popular application such as- Soft Robotics, Robotics grippers and artificial muscles.

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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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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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Soft Robotic Gripper Based on Multi-Layers of Dielectric Elastomer Actuators

Journal of Robotics and Mechatronics ◽

10.20965/jrm.2021.p0968 ◽

2021 ◽

Vol 33 (4) ◽

pp. 968-974

Author(s):

Witchuda Thongking ◽

Ardi Wiranata ◽

Ayato Minaminosono ◽

Zebing Mao ◽

Shingo Maeda ◽

...

Keyword(s):

Response Time ◽

Low Cost ◽

Fast Response ◽

Dielectric Elastomer ◽

Heel Strike ◽

Soft Robotics ◽

Artificial Muscles ◽

Light Weight ◽

Dielectric Elastomer Actuators ◽

The Relationship

Dielectric elastomer actuators (DEAs) are a promising technology for soft robotics. The use of DEAs has many advantages, including light weight, resilience, and fast response for its applications, such as grippers, artificial muscles, and heel strike generators. Grippers are commonly used as grasping devices. In this study, we focus on DEA applications and propose a technology to expand the applicability of a soft gripper. The advantages of gripper-based DEAs include light weight, fast response, and low cost. We fabricated soft grippers using multiple DEA layers. The grippers successfully held or gripped an object, and we investigated the response time of the grippers and their angle characteristics. We studied the relationship between the number of DEA layers and the performance of our grippers. Our experimental results show that the multi-layered DEAs have the potential to be strong grippers.

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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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Soft Freestanding Planar Artificial Muscle Based on Dielectric Elastomer Actuator

Journal of Applied Mechanics ◽

10.1115/1.4039289 ◽

2018 ◽

Vol 85 (5) ◽

Cited By ~ 7

Author(s):

Lei Qin ◽

Jiawei Cao ◽

Yucheng Tang ◽

Jian Zhu

Keyword(s):

Structural Complexity ◽

Artificial Muscle ◽

High Energy ◽

Dielectric Elastomer ◽

Tactile Feedback ◽

High Energy Density ◽

Artificial Muscles ◽

Dielectric Elastomer Actuators ◽

Electromechanical Instability ◽

Compression Springs

Dielectric elastomer actuators (DEAs) exhibit interesting muscle-like attributes including large voltage-induced deformation and high energy density, thus can function as artificial muscles for soft robots/devices. This paper focuses on soft planar DEAs, which have extensive applications such as artificial muscles for jaw movement, stretchers for cell mechanotransduction, and vibration shakers for tactile feedback, etc. Specifically, we develop a soft planar DEA, in which compression springs are employed to make the entire structure freestanding. This soft freestanding actuator can achieve both linear actuation and turning without increasing the size, weight, or structural complexity, which makes the actuator suitable for driving a soft crawling robot. Furthermore, its simple structure and homogeneous deformation allow for analytic modeling, which can be used to interpret the large voltage-induced deformation and interesting mechanics phenomenon (i.e., wrinkling and electromechanical instability). A preliminary demonstration showcases that this soft planar actuator can be employed as an artificial muscle to drive a soft crawling robot.

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Multiple Inputs-Single Accumulated Output Mechanism for Soft Linear Actuators

Journal of Mechanisms and Robotics ◽

10.1115/1.4041632 ◽

2018 ◽

Vol 11 (1) ◽

Cited By ~ 1

Author(s):

Kyeong Ho Cho ◽

Ho Moon Kim ◽

Youngeun Kim ◽

Sang Yul Yang ◽

Hyouk Ryeol Choi

Keyword(s):

Artificial Muscle ◽

Operating Mode ◽

Robotic Arm ◽

Soft Actuator ◽

Wearable Robots ◽

Working Principle ◽

Linear Actuators ◽

Soft Actuators ◽

Muscle Actuators ◽

Further Development

Soft linear actuators (SLAs) such as shape memory alloy (SMA) wires, pneumatic soft actuators, dielectric elastomer actuator, and twisted and coiled soft actuator (TCA) called artificial muscle actuators in general, have many advantages over the conventional actuators. SLAs can realize innovative robotic technologies like soft robots, wearable robots, and bionic arms in the future, but further development is still needed in real applications because most SLAs do not provide large displacement or force as needed. This paper presents a novel mechanism supplementing SLAs by accumulating the displacement of multiple SLAs. It adopts the principle of differential gears in reverse. Since the input units of the mechanism are extensible, more displacement can be accumulated by increasing the number of the input units as many as needed. The mechanism is basically used to accumulate displacements, but can be used to accumulate forces by changing its operating mode. This paper introduces the design and working principle of the mechanism and validates its operation experimentally. In addition, the mechanism is implemented on a robotic arm and its effectiveness is confirmed.

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Dielectric Elastomer Actuator Driven Soft Robotic Structures With Bioinspired Skeletal and Muscular Reinforcement

Frontiers in Robotics and AI ◽

10.3389/frobt.2020.510757 ◽

2020 ◽

Vol 7 ◽

Author(s):

M. Franke ◽

A. Ehrenhofer ◽

S. Lahiri ◽

E.-F. M. Henke ◽

T. Wallmersperger ◽

...

Keyword(s):

Degrees Of Freedom ◽

Aerosol Deposition ◽

Dielectric Elastomer ◽

Artificial Muscles ◽

Soft Systems ◽

Natural Motion ◽

Dielectric Elastomer Actuators ◽

Resonance Frequencies ◽

Wide Range ◽

Laminate Theory

Natural motion types found in skeletal and muscular systems of vertebrate animals inspire researchers to transfer this ability into engineered motion, which is highly desired in robotic systems. Dielectric elastomer actuators (DEAs) have shown promising capabilities as artificial muscles for driving such structures, as they are soft, lightweight, and can generate large strokes. For maximum performance, dielectric elastomer membranes need to be sufficiently pre-stretched. This fact is challenging, because it is difficult to integrate pre-stretched membranes into entirely soft systems, since the stored strain energy can significantly deform soft elements. Here, we present a soft robotic structure, possessing a bioinspired skeleton integrated into a soft body element, driven by an antagonistic pair of DEA artificial muscles, that enable the robot bending. In its equilibrium state, the setup maintains optimum isotropic pre-stretch. The robot itself has a length of 60 mm and is based on a flexible silicone body, possessing embedded transverse 3D printed struts. These rigid bone-like elements lead to an anisotropic bending stiffness, which only allows bending in one plane while maintaining the DEA's necessary pre-stretch in the other planes. The bones, therefore, define the degrees of freedom and stabilize the system. The DEAs are manufactured by aerosol deposition of a carbon-silicone-composite ink onto a stretchable membrane that is heat cured. Afterwards, the actuators are bonded to the top and bottom of the silicone body. The robotic structure shows large and defined bimorph bending curvature and operates in static as well as dynamic motion. Our experiments describe the influence of membrane pre-stretch and varied stiffness of the silicone body on the static and dynamic bending displacement, resonance frequencies and blocking forces. We also present an analytical model based on the Classical Laminate Theory for the identification of the main influencing parameters. Due to the simple design and processing, our new concept of a bioinspired DEA based robotic structure, with skeletal and muscular reinforcement, offers a wide range of robotic application.

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Dielectric Elastomer Fiber Actuators with Aqueous Electrode

Polymers ◽

10.3390/polym13244310 ◽

2021 ◽

Vol 13 (24) ◽

pp. 4310

Author(s):

Keita Shimizu ◽

Toshiaki Nagai ◽

Jun Shintake

Keyword(s):

Chloride Solution ◽

Water Environment ◽

Dielectric Elastomer ◽

Soft Robotics ◽

Successful Implementation ◽

Driving Frequency ◽

Silicone Tube ◽

Linear Type ◽

Dielectric Elastomer Actuators ◽

Actuation Strain

Dielectric elastomer actuators (DEAs) are one of the promising actuation technologies for soft robotics. This study proposes a fiber-shaped DEA, namely dielectric elastomer fiber actuators (DEFAs). The actuator consisted of a silicone tube filled with the aqueous electrode (sodium chloride solution). Furthermore, it could generate linear and bending actuation in a water environment, which acts as the ground side electrode. Linear-type DEFA and bending-type DEFA were fabricated and characterized to prove the concept. A mixture of Ecoflex 00–30 (Smooth-On) and Sylgard 184 (Dow Corning) was employed in these actuators for the tube part, which was 75.0-mm long with outer and inner diameters of 6.0 mm and 5.0 mm, respectively. An analytical model was constructed to design and predict the behavior of the devices. In the experiments, the linear-type DEFA exhibited an actuation strain and force of 1.3% and 42.4 mN, respectively, at 10 kV (~20 V/µm) with a response time of 0.2 s. The bending-type DEFA exhibited an actuation angle of 8.1° at 10 kV (~20 V/µm). Subsequently, a jellyfish-type robot was developed and tested, which showed the swimming speed of 3.1 mm/s at 10 kV and the driving frequency of 4 Hz. The results obtained in this study show the successful implementation of the actuator concept and demonstrate its applicability for soft robotics.

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Ethanol Phase Change Actuator Based on Thermally Conductive Material for Fast Cycle Actuation

Polymers ◽

10.3390/polym13234095 ◽

2021 ◽

Vol 13 (23) ◽

pp. 4095

Author(s):

Zirui Liu ◽

Bo Sun ◽

Jianjun Hu ◽

Yunpeng Zhang ◽

Zhaohua Lin ◽

...

Keyword(s):

Mechanical Properties ◽

Graphene Oxide ◽

Phase Change ◽

Thermal Imaging ◽

Au Nanoparticles ◽

Artificial Muscle ◽

Fast Response ◽

Artificial Muscles ◽

Thermally Conductive ◽

Mechanical Actuation

Artificial muscle actuator has been devoted to replicate the function of biological muscles, playing an important part of an emerging field at inter-section of bionic, mechanical, and material disciplines. Most of these artificial muscles possess their own unique functionality and irreplaceability, but also have some disadvantages and shortcomings. Among those, phase change type artificial muscles gain particular attentions, owing to the merits of easy processing, convenient controlling, non-toxic and fast-response. Herein, we prepared a silicon/ethanol/(graphene oxide/gold nanoparticles) composite elastic actuator for soft actuation. The functional properties are discussed in terms of microstructure, mechanical properties, thermal imaging and mechanical actuation characteristics, respectively. The added graphene oxide and Au nanoparticles can effectively accelerate the heating rate of material and improve its mechanical properties, thus increasing the vaporization rate of ethanol, which helps to accelerate the deformation rate and enhance the actuation capability. As part of the study, we also tested the performance of composite elastomers containing different concentrations of graphene oxide to identify GO-15 (15 mg of graphene oxide per 7.2 mL of material) flexible actuators as the best composition with a driving force up to 1.68 N.

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Modeling, Analysis, and Function Extension of the McKibben Hydraulic Artificial Muscles

BATH/ASME 2020 Symposium on Fluid Power and Motion Control ◽

10.1115/fpmc2020-2741 ◽

2020 ◽

Author(s):

Siqing Chen ◽

He Xu

Keyword(s):

High Pressure ◽

Theoretical Analysis ◽

Artificial Muscle ◽

Design Parameters ◽

Artificial Muscles ◽

Soft Robots ◽

The Law ◽

Soft Actuators ◽

The Impact ◽

The Relationship

Abstract Compared with rigid robots, flexible robots have soft and extensible bodies enforcing their abilities to absorb shock and vibration, hence reducing the impact of probable collisions. Due to their high adaptability and minimally invasive features, soft robots are used in various fields. The McKibben hydraulic artificial muscles are the most popular soft actuator because of the controllability of hydraulic actuator and high force to weight ratio. When its deformation reaches a certain level, the actuators can be stopped automatically without any other braking mechanism. The research of McKibben hydraulic artificial muscles is beneficial to the theoretical analysis of soft actuators in the mechanical system. The design of soft actuators with different deformations promotes the development of soft robots. In this paper, a static modeling of the McKibben hydraulic artificial muscles is established, and its correctness is verified by theoretical analysis and experiment. In this model, the deformation mechanism of the artificial muscle and the law of output force is put forward. The relationship between muscle pressure, load, deformation, and muscle design parameters is presented through the mechanical analysis of the braid, elastic tube, and sealed-end. The law of the muscle deformation with high pressure is predicted. The reason for the muscle’s tiny elongation with extremely high pressure is found through the analysis of the relationship between the angle of the braid, the length of single braided thread, and the pressure. With the increase of pressure, the angle of the braid tends to a fixed value. As the stress of braided thread increases, so does its length. The length changes obviously when the stress is extremely enormous. The angle of the braid and the length of the braided thread control the deformation of artificial muscles, resulting in a slight lengthening with extreme high pressure. Under normal pressure, the length of the braided wire is negligible, so that the entire muscle becomes shorter. According to the modeling and theoretical analysis, a new McKibben hydraulic artificial muscle that can elongate under normal rising pressure is designed. This artificial muscle can grow longer with pressure increases, eventually reaching its maximum length. During this time, its diameter barely changes. Its access pressure is higher than that of conventional elongated artificial muscles. Through experiments, the relationship between the muscle deformation, pressure, and load still conform to this theoretical model. This model can be used for the control of soft actuators and the design of new soft robots. This extensional McKibben hydraulic artificial muscles and the conventional McKibben hydraulic artificial muscles can be used in the bilateral control of soft robots.

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