Inflation-Induced Twist in Geometrically Incompatible Isotropic Tubes

2020 ◽  
Vol 88 (3) ◽  
Author(s):  
Nir Emuna ◽  
Noy Cohen
Keyword(s):  
Residual Stress ◽  
Twist Angle ◽  
Torsional Stiffness ◽  
Artificial Muscles ◽  
Induced Anisotropy ◽  
Material Anisotropy ◽  
Growth And Remodeling ◽  
Numerical Studies ◽  
Soft Actuators ◽  
Limiting Pressure

Abstract The fundamental twist motion in tubes is commonly generated by torque. However, twist can also be indirectly induced by mechanical loadings (inflation/extension), growth and remodeling processes, and environmental conditions. This unusual coupling commonly originates from material anisotropy. In this study, we propose a configuration of isotropic bilayer tubes that twists upon inflation. This mechanism is based on twist incompatibility: two tubes are axially twisted in opposing directions and glued to form a bilayer tube. The residual stress that develops gives rise to deformation-induced anisotropy, which enables twist under inflation. To demonstrate the induced-twist response, we employ the neo-Hookean and the Gent models. We derive closed-form expressions for the twist angle as a function of the pressure in neo-Hookean bilayer tubes and show that a terminal angle exists in the limiting pressure. Numerical studies of bilayer Gent tubes are carried out and reveal that the lock-up effect governs the terminal twist angle. Interestingly, we find that in bilayer Gent tubes, the twist direction and handedness can be reversed upon inflation. These counter-intuitive effects, known as inversion and perversion, respectively, stem from the load-dependent variations in the ratio between the torsional stiffness of the two layers. We provide criteria that allow to program the induced twist response of bilayer tubes through the design of the properties of the two layers. This approach may be of value in the design of soft robots, artificial muscles, and soft actuators.

Flutter of Perforated Metallic Plates Repaired with Cross-Ply Composite Patches

2009 ◽  
Vol 417-418 ◽  
pp. 709-712
Author(s):  
Ali Amin Yazdi ◽  
Jalil Rezaeepazhand
Keyword(s):  
Laminated Composite ◽  
Material Anisotropy ◽  
Perforated Plates ◽  
Closed Form Solutions ◽  
Finite Element Software ◽  
Composite Patch ◽  
Numerical Studies ◽  
Flutter Analysis ◽  
Flutter Boundary ◽  
Metallic Plates

This study investigates the application of laminated composite patches for enhancement of flutter behavior of perforated metallic plates repaired with an external composite patch. Due to material anisotropy and discontinuity in geometry involved in flutter analysis of repaired plates, closed form solutions are practically unobtainable. Numerical studies using commercial finite element software were conducted to investigate the effects of variation in lamination parameters on the flutter boundary of perforated plates repaired with cross-ply composite patches. Both ply-level and sub-laminate level configurations are investigated. Presented results illustrate that flutter boundaries of perforated plates can be changed by choosing proper stacking sequence for composite patches.

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

Actuators ◽  
2018 ◽  
Vol 7 (4) ◽  
pp. 73 ◽  
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.

scholarly journals Graphene/silver nanoflower hybrid coating for improved cycle performance of thermally-operated soft actuators

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Chengxu Piao ◽  
Ji Won Suk
Keyword(s):  
High Performance ◽  
Hybrid Coating ◽  
Cycle Performance ◽  
Artificial Muscles ◽  
Pristine Graphene ◽  
Pulsed Current ◽  
Enhanced Heat Transfer ◽  
Graphene Flakes ◽  
Sewing Threads ◽  
Soft Actuators

Abstract Twisted and coiled actuators (TCAs), fabricated by twisting cheap nylon sewing threads, have attracted a great deal of attention for their use as artificial muscles or soft actuators. Since the dynamic behavior of a thermally-operated TCA is governed by its thermal properties, graphene and silver nanoflowers (AgNFs) were spray-coated onto the surface of an actuator to achieve enhanced heat transfer. Addition of AgNFs improves interfacial thermal contacts between graphene flakes, while pristine graphene flakes have extremely high in-plane thermal conductivity. Thus, the synergistic effect of graphene and AgNFs reduced the total cycle time of the TCA by up to 38%. Furthermore, when a pulsed current with a 40% duty cycle was applied to the TCA, the graphene/AgNF-coated TCA exhibited a threefold larger peak-to-peak amplitude of the displacement oscillation of the actuator, as compared to that of the non-coated TCA, which demonstrates that the combination of graphene and AgNFs effectively reduced a cooling time of the TCA. This work shows great potential for a simple coating of graphene and AgNFs to produce high-performance thermally-operated soft actuators.

Torsional Stiffness Improvement of a Soft Pneumatic Finger Using Embedded Skeleton

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Amin Lotfiani ◽  
Huichan Zhao ◽  
Zhufeng Shao ◽  
Xili Yi
Keyword(s):  
Torsional Stiffness ◽  
Good Precision ◽  
Pneumatic Actuators ◽  
Finite Element Approach ◽  
Grasping And Manipulation ◽  
Element Approach ◽  
Series Of Experiments ◽  
Soft Actuators ◽  
Compact Design ◽  
Rigid Skeleton

Abstract Silicone-based pneumatic actuators are among the most widely used soft actuators in adaptable fingers. However, due to the soft nature of silicone, the performance of these fingers is highly affected by the low torsional stiffness, which may cause failure in grasping and manipulation. To address this problem, a compact design is proposed by embedding a rigid skeleton into a soft pneumatic finger. A finite element approach with an analysical model is used to evaluate the performance of the fingers both with and without the skeleton. Then, a series of experiments is performed to study the bending motion and rigidity of the fingers. The results reveal that the skeleton increases the torsional stiffness of the finger up to 300%. Furthermore, the consistency with the experimental data indicates the good precision of the proposed modeling method. Finally, a two-finger hand is designed to evaluate the performance of the reinforced finger in reality. The grasp experiments illustrate that the hybrid finger with the skeleton is highly adaptable and can successfully grasp and manipulate heavy objects. Thus, a potential approach is proposed to improve the torsional stiffness of silicone-based pneumatic fingers while maintaining adaptability.

scholarly journals Modeling and System Integration for a Thin Pneumatic Rubber 3-DOF Actuator

Actuators ◽  
2019 ◽  
Vol 8 (2) ◽  
pp. 32 ◽  
Author(s):  
Shuhei Kawamura ◽  
Mizuki Sudani ◽  
Mingcong Deng ◽  
Yuichi Noge ◽  
Shuichi Wakimoto
Keyword(s):  
System Integration ◽  
Degrees Of Freedom ◽  
Small Diameter ◽  
Experimental System ◽  
Longitudinal Direction ◽  
Axial Direction ◽  
Artificial Muscles ◽  
Contraction Force ◽  
Proposed Model ◽  
Soft Actuators

Recently, soft actuators have been getting increased attention within various fields. The actuators are composed of flexible materials and driven by pneumatic pressure. A thin pneumatic rubber actuator generating 3 degrees of freedom motion, called 3-DOF micro-hand, has small diameter McKibben artificial muscles which generate a contraction force in the axial direction. By this structure, the micro-hand contracts in the longitudinal direction and bends in any direction by changing the applied air pressure pattern to the artificial muscles. The input–output relation of the micro-hand, however, is complicated and has not been modeled. In this paper, modeling for 3-DOF micro-hand is proposed. Moreover, the experimental system is built for the micro-hand and the proposed model is evaluated by using the experimental results.

scholarly journals Dielectric Elastomer Actuator for Soft Robotics Applications and Challenges

2020 ◽  
Vol 10 (2) ◽  
pp. 640 ◽  
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.

scholarly journals Dielectric Elastomer Grippers

2021 ◽  
Vol 10 (5) ◽  
pp. 33-36
Author(s):  
Mills Patel ◽  
Rudrax Khamar ◽  
Akshat Shah ◽  
Tej shah ◽  
Bhavik Soneji
Keyword(s):  
Mechanical Properties ◽  
Power Generation ◽  
State Of The Art ◽  
Artificial Muscle ◽  
Dielectric Elastomer ◽  
Soft Robotics ◽  
Artificial Muscles ◽  
Dielectric Elastomer Actuators ◽  
Working Principle ◽  
Soft Actuators

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.

scholarly journals Electroactive Polymers Obtained by Conventional and Non-Conventional Technologies

Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2713
Author(s):  
Akel F. Kanaan ◽  
Ana C. Pinho ◽  
Ana P. Piedade
Keyword(s):  
Electroactive Polymers ◽  
Polymer Processing ◽  
Processing Technique ◽  
Electrical Stimulus ◽  
Smart Devices ◽  
Artificial Muscles ◽  
Electromechanical Properties ◽  
Novel Approach ◽  
Materials Used ◽  
Soft Actuators

Electroactive polymers (EAPs), materials that present size/shape alteration in response to an electrical stimulus, are currently being explored regarding advanced smart devices, namely robotics, valves, soft actuators, artificial muscles, and electromechanical sensors. They are generally prepared through conventional techniques (e.g., solvent casting and free-radical polymerization). However, non-conventional processes such as those included in additive manufacturing (AM) are emerging as a novel approach to tune and enhance the electromechanical properties of EAPs to expand the scope of areas for this class of electro-responsive material. This review aims to summarize the published work (from the last five years) in developing EAPs either by conventional or non-conventional polymer processing approaches. The technology behind each processing technique is discussed as well as the main mechanism behind the electromechanical response. The most common polymer-based materials used in the design of current EAPs are reviewed. Therefore, the main conclusions and future trends regarding EAPs obtained by conventional and non-conventional technologies are also given.

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

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.

Estimation of ion dimension doped in conducting polymers electrochemically

MRS Advances ◽  
2018 ◽  
Vol 3 (27) ◽  
pp. 1543-1549 ◽  
Author(s):  
Keiichi Kaneto ◽  
Fumito Hata ◽  
Sadahito Uto
Keyword(s):  
Conducting Polymers ◽  
Electrochemical Oxidation ◽  
Artificial Muscles ◽  
Counter Ions ◽  
Laser Displacement Meter ◽  
Polypyrrole Film ◽  
Soft Actuators ◽  
Ion Size ◽  
Isotropic Expansion ◽  
The Relationship

ABSTRACTElectroactive conducting polymers are suitable for soft actuators (artificial muscles). The actuation is induced by electrochemical oxidation of conducting polymer (film) in an electrolyte solution, due to insertion of bulky counter ions (dopant ions). The magnitude of deformation (strain) depends on the size of dopant ions and the degree of oxidation. It is worthwhile to know the relationship between the magnitudes of deformation and ion size. An electrodeposited Polypyrrole film was electrochemically cycled in aqueous electrolytes of NaCl, NaBr, NaNO3, NaBF4 and NaClO4. The strain of film during electrochemical oxidation and reduction was precisely measured using a laser displacement meter and a handmade apparatus. From the strain and electrical charges inserted in the film during oxidation, the volumes and radii of dopant ions were estimated, assuming the isotropic expansion of the film. The estimated anion radii of Cl-, Br-, NO3-, BF4- and ClO4- were 235, 246, 250, 270 and 290, respectively. The results were discussed taking the crystallographic and hydrated ion radii in literatures into consideration.

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