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Novel Dielectric Elastomer Actuator Configurations And Devices For Soft Robotic And Wearable Applications
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Book Synopsis Novel Dielectric Elastomer Actuator Configurations and Devices for Soft Robotic and Wearable Applications by : Roshan Joseph Plamthottam
Download or read book Novel Dielectric Elastomer Actuator Configurations and Devices for Soft Robotic and Wearable Applications written by Roshan Joseph Plamthottam and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soft robotic devices require highly stretchable and flexible materials to ensure that they can conform to delicate objects and work safely alongside humans. As a result, new flexible actuation technologies must be developed so that soft robotic platforms can achieve their desired function. Dielectric elastomer actuators are an emerging actuator technology that possesses high energy density in a lightweight package. However, since these actuators utilize a thin, soft elastomer film, they are particularly delicate and depending on their configuration, do not efficiently outcouple their outputted mechanical energy. Rigid frames, metallic springs, and other mechanisms have been used in the past to improve the performance of these actuators in various configurations, but these highly stiff components are not ideal for soft robotic applications. Novel strategies can be implemented to mitigate these issues. In this work, we highlight new strategies to create novel dielectric elastomer actuator configurations with high power density, large strokes, and high force output. First, we discuss the development of a core-free rolled dielectric elastomer. We then discuss a flexible DEA-based fluidic pump that can output high flowrates and withstand large pressures for its small size. Finally, we detail a novel mechanism to control the deformation direction of DEAs, and leverage this mechanism to create a patch-like haptic interface for virtual reality applications.
Book Synopsis Large Deformable Soft Actuators Using Dielectric Elastomer and Origami Inspired Structures by : JangHo Park
Download or read book Large Deformable Soft Actuators Using Dielectric Elastomer and Origami Inspired Structures written by JangHo Park and published by . This book was released on 2019 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt: "There have been significant developments in the field of robotics. Significant development consists of new configurations, control mechanisms, and actuators based upon its applications. Despite significant improvements in modern robotics, the biologically inspired robots has taken the center stage. Inspired by nature, biologically inspired robots are called ‘soft robots’. Within these robots lies a secret ingredient: the actuator. Soft robotic development has been driven by the idea of developing actuators that are like human muscle and are known as ‘artificial muscle’. Among different materials suitable for the development of artificial muscle, the dielectric elastomer actuator (DEA) is capable of large deformation by applying an electric field. Theoretical formulation for DEA was performed based upon the constitutive hyperelastic models and was validated by using finite element method (FEM) using ABAQUS. For FEM, multistep analysis was performed to apply pre-stretch to the membrane before applying actuation voltage. Based on the validation of DEA, different configurations of DEA were investigated. Helical dielectric elastomer actuator and origami dielectric elastomer actuator were investigated using theoretical modeling. Comparisons were made with FEM to validate the model. This study focus on the theoretical and FEM analysis of strain within the different configuration of DEA and how the actuation strain of the dielectric elastomer can be translated into contraction and/or bending of the actuator."--Abstract.
Download or read book Soft Actuators written by Kinji Asaka and published by Springer. This book was released on 2014-11-17 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt: The subject of this book is the current comprehensive research and development of soft actuators, and encompasses interdisciplinary studies of materials science, mechanics, electronics, robotics and bioscience. As an example, the book includes current research on actuators based on biomaterials to provide future perspectives for artificial muscle technology. Readers can obtain detailed, useful information about materials, methods of synthesis, fabrication and measurements. The topics covered here not only promote further research and development of soft actuators but also lead the way to their utilization and industrialization. One outstanding feature of the book is that it contains many color figures, diagrams and photographs clearly describing the mechanism, apparatus and motion of soft actuators. The chapter on modeling is conducive to more extensive design work in materials and devices and is especially useful in the development of practical applications. Readers can acquire the newest technology and information about the basic science and practical applications of flexible, lightweight and noiseless soft actuators, which are quite unlike conventional mechanical engines and electric motors. The new ideas offered in this volume will provide inspiration and encouragement to researchers and developers as they explore new fields of applications for soft actuators.
Book Synopsis Dielectric Elastomers as Electromechanical Transducers by : Federico Carpi
Download or read book Dielectric Elastomers as Electromechanical Transducers written by Federico Carpi and published by Elsevier. This book was released on 2011-09-06 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dielectric Elastomers as Electromechanical Transducers provides a comprehensive and updated insight into dielectric elastomers; one of the most promising classes of polymer-based smart materials and technologies. This technology can be used in a very broad range of applications, from robotics and automation to the biomedical field. The need for improved transducer performance has resulted in considerable efforts towards the development of devices relying on materials with intrinsic transduction properties. These materials, often termed as “smart or “intelligent , include improved piezoelectrics and magnetostrictive or shape-memory materials. Emerging electromechanical transduction technologies, based on so-called ElectroActive Polymers (EAP), have gained considerable attention. EAP offer the potential for performance exceeding other smart materials, while retaining the cost and versatility inherent to polymer materials. Within the EAP family, “dielectric elastomers , are of particular interest as they show good overall performance, simplicity of structure and robustness. Dielectric elastomer transducers are rapidly emerging as high-performance “pseudo-muscular actuators, useful for different kinds of tasks. Further, in addition to actuation, dielectric elastomers have also been shown to offer unique possibilities for improved generator and sensing devices. Dielectric elastomer transduction is enabling an enormous range of new applications that were precluded to any other EAP or smart-material technology until recently. This book provides a comprehensive and updated insight into dielectric elastomer transduction, covering all its fundamental aspects. The book deals with transduction principles, basic materials properties, design of efficient device architectures, material and device modelling, along with applications. Concise and comprehensive treatment for practitioners and academics Guides the reader through the latest developments in electroactive-polymer-based technology Designed for ease of use with sections on fundamentals, materials, devices, models and applications
Book Synopsis Modelling of Dielectric Elastomer Actuators and Application to Soft Robots by : 李泽州
Download or read book Modelling of Dielectric Elastomer Actuators and Application to Soft Robots written by 李泽州 and published by . This book was released on 2020 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Soft Robotics in Rehabilitation by : Amir Jafari
Download or read book Soft Robotics in Rehabilitation written by Amir Jafari and published by Academic Press. This book was released on 2021-02-20 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soft Robotics in Rehabilitation explores the specific branch of robotics dealing with developing robots from compliant and flexible materials. Unlike robots built from rigid materials, soft robots behave the way in which living organs move and adapt to their surroundings and allow for increased flexibility and adaptability for the user. This book is a comprehensive reference discussing the application of soft robotics for rehabilitation of upper and lower extremities separated by various limbs. The book examines various techniques applied in soft robotics, including the development of soft actuators, rigid actuators with soft behavior, intrinsically soft actuators, and soft sensors. This book is perfect for graduate students, researchers, and professional engineers in robotics, control, mechanical, and electrical engineering who are interested in soft robotics, artificial intelligence, rehabilitation therapy, and medical and rehabilitation device design and manufacturing. Outlines the application of soft robotic techniques to design platforms that provide rehabilitation therapy for disabled persons to help improve their motor functions Discusses the application of soft robotics for rehabilitation of upper and lower extremities separated by various limbs Offers readers the ability to find soft robotics devices, methods, and results for any limb, and then compare the results with other options provided in the book
Book Synopsis Material Characterization of a Dielectric Elastomer for the Design of a Linear Actuator by : Alexander Tristan Helal
Download or read book Material Characterization of a Dielectric Elastomer for the Design of a Linear Actuator written by Alexander Tristan Helal and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Electrical motors and/or hydraulics and pneumatics cylinders are commonly used methods of actuation in mechanical systems. Over the last two decades, due to arising market needs, novel self-independent mobile systems such as mobility assistive devices have emerged with the help of new advancements in technology. The actuation criteria for these devices differ greatly from typical mechanical systems, which has made the implementation of classical actuators difficult within modern assistive devices. Among the numerous challenges, limited energy storage capabilities by mobile systems have restricted their achievable operational time. Furthermore, new expectations for device weight and volume, as well as actuator structural compliance, have added to this quandary. Electroactive polymers, a category of smart materials, have emerged as a strong contender for the use in low-cost efficient actuators. They have demonstrated great potential in soft robotic and assistive device/prosthetic applications due to their actuation potential and similar mechanical behaviour to human skeletal muscles. Dielectric Elastomers, in particular, have shown very promising properties for these types of applications. Their structures have shown large achievable deformation, while remaining light-weight, mechanically efficient, and low-cost. This thesis aims to characterize, and model the behaviour of 3MTM VHB polyacrylic dielectric elastomer, in order to establish a foundation for its implementation in a proposed novel linear actuator concept. In this thesis, a comprehensive experimental evaluation is accomplished, which resulted in the better understanding of the elastomer's biaxial mechanical and electro-mechanically coupled behaviours. Subsequently, a constitutive biaxial mechanical model was derived in order to provide a predictive design equation for future actuator development. This model proved effective in providing a predictive tool for the biaxial mechanical tensile response of the material. Finally, a simplified prototype was devised as a proof of concept. This first iteration applied experimental findings to validate the working principles behind the proposed actuator design. The results confirmed the proof of concept, through achieved reciprocal linear motion, and provided insight into the design considerations for prototype optimization and final actuator development.
Book Synopsis Modeling of a Dielectric Elastomer by : Mesfer Alkhathami
Download or read book Modeling of a Dielectric Elastomer written by Mesfer Alkhathami and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Dielectric elastomer actuator (DEA) is a key element for the soft robots, which has received increasing attention. However, the main difficulties in modeling soft actuators such as dielectric elastomer actuators are time-dependent viscoelasticity and their material nonlinearity. It is important to consider the viscoelasticity of the dielectric elastomer (DE) to fully understand its mechanical behavior. However, so far only a few works have been presented considering the viscoelasticity of the DE material together with the effect of temperature and deformation. In this thesis, a dynamic electromechanical-coupled model for a rectangle dielectric elastomer a commonly used material (the acrylic elastomer VHB 4910) has been proposed, with taking into consideration of the influence of temperature, voltage, and frequency on the DE. The proposed model is based on the free energy physical-based principle, where the general Kelvin-Voigt model is applied to describe the viscoelasticity of the DE, and the Maxwell force together with the Electrostrictive force are considered. The influence of temperature and deformation on the DE is included in this model. The model in this study is a dynamic electromechanical model of a DE actuator, and can effectively describe the dynamic characteristics of the DE. By using the Differential Evolution, the model parameters were identified. The model was implemented and simulated in MATLAB, and the simulation and the actual experiment agrees to a great extent. The experimental test conducted in this study matches with the simulations results, which means that the proposed model can be practical to predict and describe DEAs electromechanical and viscoelastic behavior. Predicting the electromechanical and viscoelastic behavior of the DE is extremely useful for controlling a viscoelastic DEA and paving the way to improve the control performance, and also develops applications in soft robotics.
Download or read book HSC Football 20 Year Reunion written by and published by . This book was released on 1988* with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: Newspaper clippings chronicle the 1968 season of the Humboldt State Lumberjack football team.
Book Synopsis Bioinspired Liquid Crystal Elastomer (LCE) Based Soft Actuators with Multimodal Actuation by : Qiguang He
Download or read book Bioinspired Liquid Crystal Elastomer (LCE) Based Soft Actuators with Multimodal Actuation written by Qiguang He and published by . This book was released on 2021 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt: Inspired by the biology, soft robots have drawn tremendous attention due to its large and continuous deformation, friendly human-machine interaction, large number of degrees of freedom (DOFs), capability of absorbing energy. They have been explored in broad applications ranging from dexterous soft gripper to the novel assistive devices. In the recent decade, numerous soft actuating materials and deformable structures have been developed to construct soft robots, including hydrogels, shape memory polymers (SMPs), dielectric elastomer actuators (DEAs), fluid elastomer actuators (FEAs) and magnetic actuators. However, those materials and structures have well-known limitations such as slow actuation speed, irreversibility, high voltage input and bulky controlling systems. Liquid crystal elastomers (LCEs), as newly emerging soft actuating materials, exhibit large and reversible deformation and versatile actuation modes. Based on the molecular structure, LCE can be viewed as a combination of liquid crystal molecules and polymer networks. When the LCE is heated above the critical temperature, it can generate large deformation because of the nematic-isotropic phase transition. However, in terms of the practical use of LCE, a few challenges exist such as lack of programmable operation and slow responsive speed for LCEs, which need to be addressed. In this dissertation, we first integrate flexible heating wire into LCE tube, forming electrically controlled soft tubular actuator. By selectively applying low electrical voltage, this soft tubular actuator can exhibit multiple actuation modes, such as different directional bending and homogeneous contraction. The LCE soft tubular actuator can also be integrated to construct untethered robot that can execute multiple functionalities. To address the slow responsive speed of LCE based soft actuator, we embed microfluidic channel into LCE, forming vascular LCE soft actuator. Through alternatively injecting hot and cold fluid into its internal fluidic channel, the vascular LCE soft actuator can generate fast actuation as well as recovery. In addition, by introducing the disulfide bonds into the LCE materials, the newly obtained vascular LCE based soft actuator has shown repairability and recyclability. Finally, we use electrospinning technique to fabricate LCE microfiber that can be actuated by NIR light. We demonstrate that the electrospun LCE fiber can be easily integrated to micro-robotic system and machine as artificial muscle fiber.
Book Synopsis Novel Bidirectional Actuator Development Using Elastomeric Materials and Magnets by : Moises Gomez
Download or read book Novel Bidirectional Actuator Development Using Elastomeric Materials and Magnets written by Moises Gomez and published by . This book was released on 2020 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The objective of this thesis was to develop a novel bidirectional soft actuator for use in bioinspired and wearable robotic devices by investigating the effects that electromagnetic and material properties have on displacement. Findings from the thesis have the potential to significantly advance the field of soft robotics by demonstrating the viability of using elastomeric materials and magnetic fields as the driving mechanism for a new soft actuation method. The three primary aims were to develop uniform electromagnetic coils for actuation, to create soft cores to be combined with the electromagnetic coils to bolster the magnetic field and to study the displacement of the embedded assembly in an elastomeric material, effectively creating a soft solenoid capable of bidirectional actuation. In practice, this was a success. The winding process for coils was improved for creating uniform coils with a 3D printed winder and the cores were tested for their magnetic field strength based on varying weight fraction of particles. Two final actuators were made to test for differences in displacement based on mixing ratio changes in the material fabrication processes. Ecoflex 00-20, (Smooth-On Inc.: Macungie, PA) made using a 1A:1B mixing ratio, was found to perform approximately 25.2% better in compression and about 52.5% better in repulsion (based on average values) than the actuator made using a 1A:2B ratio. The final device was capable of average displacement values of 0.135 mm in compression and 0.158 mm in repulsion."--Abstract.
Book Synopsis Implementation of Soft Lithography for the Fabrication of Stacked Dielectric Elastomer Actuators for Soft Robotics by : Mert Corbaci
Download or read book Implementation of Soft Lithography for the Fabrication of Stacked Dielectric Elastomer Actuators for Soft Robotics written by Mert Corbaci and published by . This book was released on 2018 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: "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. This study presents a novel approach inspired by the natural skeletal muscles to overcome the drawbacks of conventional DEAs. 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. Soft lithography and other microfabrication techniques were utilized to allow fabrication of silicone based multilayer stacked DEA structures, composed of hundreds of micro-sized DEA units with mechanically compliant electrodes. Experiments show that free-standing multilayer DEA structures can be fabricated using existing microfabrication tools. Three fabrication approaches, using spin coating, film casting and injection molding were evaluated to improve the repeatability of the fabrication process. Multi-layer DEA fibers can be actuated in sub-kV range while maintaining actuation ratio above 5%."--Abstract.
Book Synopsis Modeling, Processing, and Characterization of Dielectric Elastomer Actuators and Sensors by : Kevin Kadooka
Download or read book Modeling, Processing, and Characterization of Dielectric Elastomer Actuators and Sensors written by Kevin Kadooka and published by . This book was released on 2017 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past two decades, electroactive polymers (EAP) have been studied as a material for soft actuator and sensor systems. Dielectric elastomers (DE) are an EAP material which relies on the electrostatic force produced on compliant electrodes to produce deformation. In the converse sense, DE sensors can be used by measuring the electrical energy or impedance change produced under deformation. The two key limitations barring DE from commercial use are high driving voltage, and low output force. The scope of this work is as follows: to improve upon these two limitations by processing of actuators by a pneumatic dispenser, by adding tactile sensing and variable stiffness properties to the actuators, and developing a mechanical model to predict the actuator behavior. This work focuses specifically on the unimorph dielectric elastomer actuator (DEA), which consists of a DE laminate which contracts in the thickness direction and expands in-plane under applied voltage, and is constrained on one face by a passive material, resulting in bending of the structure. The first part of the work is devoted to fabrication, modeling, and characterization of multilayer unimorph DEA. Fabrication is done using two schemes – the first is a conventional one, using commercially available DE films, and the second is a novel method using a robotic dispenser system. The latter technique has two objectives. The first is to reduce the thickness of the DE layers to reduce driving voltage, since the DE deformation is proportional to the square of the applied electric field which itself is inversely proportional to electrode separation. The second is to deposit higher-performance DE materials, in this case, PVDF terpolymer, which exhibits large actuation stresses because of its high dielectric constant and relatively high Young’s modulus. Using the dispenser, DE layers with 10 μm thick layers are repeatably produced, requiring actuation voltages one order of magnitude less than conventional thick DE films. Standard deviation of displacement and blocking force do not exceed 10% and 15% of the mean after 2 minutes of deformation, respectively. Elastic and viscoelastic models are developed for multilayer unimorph DEA consisting of flat and curved geometries. Both models were validated in comparison with experimental data with the latter shown to agree with the experimental data to within one standard deviation of the mean for majority of the deformation. The second section demonstrates the novel use of electrolaminates to create variable stiffness DEA (VSDEA). Variable stiffness structures are of particular interest for soft actuators, because they allow switching between a low stiffness, high displacement mode and a high stiffness mode with large holding force. One device is demonstrated by simply utilizing the passive layer of a DEA as part of an electrolaminate, allowing for four-fold increase in bending rigidity. Another device is demonstrated consisting of a bundle of parallel DEA with electrostatic chucking features to modulate shear strength of the interfaces. This device exhibits a 39-fold increase in stiffness, and a claw actuator using these actuators is capable of lifting an object 17 times its own weight. The final part of this work investigates two novel tactile sensors based on dielectric elastomers (DES). The first uses a dome-shaped protrusion to redistribute tactile forces onto an array of four capacitive sensors. The change in capacitance of the four sensors is used to measure and discriminate the force components of the impinging force. An array of these dome DES are fabricated using the dispenser system, and the ability to differentiate between normal and shear forces was demonstrated, as well as its proximity sensing ability. The tactile sensor array is also shown integrated as the passive layer of a DEA, providing tactile and proximity sensing capability to the actuator. The second tactile sensor features high resolution and scalability, and is built in to a medical assistive device coined the “artery mapper” and is used to determine the location of a target artery for arterial line placement. It is demonstrated locating an artery on a test subject, possible due to its force resolution on the order of 2.8 kPa.
Book Synopsis Dielectric Elastomers for Actuation and Energy Harvesting by : Paul A. Brochu
Download or read book Dielectric Elastomers for Actuation and Energy Harvesting written by Paul A. Brochu and published by . This book was released on 2012 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dielectric elastomers are an emerging transducer technology that fit an interesting niche. They are soft and compliant by nature, and can be stretched, either via mechanical or electrically-induced means, to very large strains. They are capable of large strains, high energy densities, and low costs, while possessing the additional advantages of being light weight and conformable. Dielectric elastomers are well suited for both actuator and generator applications, with the actuators being heralded as artificial muscles. There remains, however, several issues that prevent the widespread adoption of dielectric elastomer technology. Each applications has its set of technical issues; for actuator purposes, the primary issues are that the driving voltage required for high performance is in excess of 2000 V for most dielectric elastomer actuators, and that the lifetime when operated at high performance levels is rather short. The requirement to prestrain the elastomers to achieve high performance actuation in most cases can also add significant bulk and mass to the actuator as well as reduce its shelf-life. Thus, materials capable of high-strain performance without the requirement for prestrain are sought after. The ability to operate over a wide range of temperatures and environmental conditions, as well as operate over a wide range of frequencies, is also very important for most actuator applications. The first part of this dissertation looks to tackle the aforementioned issues. Silicone materials are chosen as the base dielectric elastomer material as they are generally capable of operating over wide ranges of temperature and frequency and are generally unaffected by moisture and have good environmental stability. The work focuses on free-standing linear soft silicone actuators as this configuration is the most relevant for real applications. A particular soft silicone has been isolated a good candidate and was extensively tested in a free-standing linear actuator configuration to determine the effects of pre-stretch and the application of mechanical loads on its actuation performance. It is shown that when the mechanical loads are properly applied, large linear actuation strains of 120% and work density of 0.5 J/cm3 can be obtained. Furthermore, we demonstrate that when coupled with single wall carbon nanotube (SWNT) compliant electrodes, fault-tolerance is introduced via self-clearing leading to significantly improved operational reliability. Driven at moderate electric fields, the actuators display relatively high linear actuation strain (25%) without degradation of the electromechanical performance even after 85,000 cycles. An issue related to the use of soft silicone actuators is that the work density is not very high when compared with many of the high-performance dielectric elastomer materials available. It is shown that the force output and work density of soft silicone actuators can be significantly enhanced by the addition of high permittivity titanium oxide nanoparticles. The nanocomposites are capable of maintaining the actuation strain performance of the pure silicone at relatively low electric fields while increasing the force output and work density due to the additive effects of mechanical reinforcement and permittivity enhancement. The high performance of the aforementioned soft silicone actuators requires the application of rather large levels of prestrain. In order to eliminate this requirement a novel all-silicone prestrain-locked interpenetrating polymer network (S-IPN) elastomer was developed. The elastomer is fabricated using a combination of two silicones: a soft room temperature vulcanizing silicone that serves as the host elastomer matrix, and a more rigid high temperature vulcanizing silicone that acts to preserve the prestrain in the host network. The free-standing prestrain-locked silicones show a more than twofold performance improvement over standard free-standing silicone films, with a linear strain of 25% and an area strain of 45% when tested in a diaphragm configuration. The S-IPN procedure was leveraged to improve electrode adhesion and stability as well as improve the interlayer adhesion in multilayer actuators. It is demonstrated that strongly bonded SWNT electrodes are capable of fault tolerance through self-clearing, even in multilayer actuators. The fault-tolerance and improved interlayer adhesion was used to fabricate prestrained free-standing silicone actuators capable of stable long life actuation (>30,000 cycles at>20% strain and>500 cycles at ~40% strain) while driving a load. Issues related to gradual electrode degradation are also addressed through the use of quasi-buckled electrodes. For generator purposes, the primary concerns are ensuring environmental stability, increasing energy density, lowering losses, and determining effective methods to couple the dielectric elastomer to natural energy sources. The factors that affect the energy density and efficiency are explored and it is found that energy density can be increased by applying larger mechanical strains and using stiffer materials. Increasing the permittivity of the material and bias voltage can also improve the energy density but reach a peak and decrease the energy density thereafter. The efficiency is shown to depend primarily on the shape of the stress-strain curve of the material, the applied strain, and a lumped parameter containing the stiffness, permittivity and nominal bias electric field. For a particular applied strain, the efficiency shows a peak at a particular value of the lumped parameter. Increasing stiffness shifts the location of the peak to higher values, and thus higher required electric fields, while increasing permittivity shifts it to lower values, and thus to lower electric fields. Using the results of this analysis, two material systems are explored: VHB acrylic elastomers at various prestrains and with various amounts of a stiffening additive, and a high energy density silicone-TiO2 nanocomposite elastomer with various amounts of additive. It is shown that increasing prestrain in the VHB acrylic system increases the energy density, while the stiffening additive has the effect of making the acrylic stiffer but results in increased losses, result in poorer performance. The silicone TiO2 composite demonstrates an increase in permittivity and stiffness with increasing additive while maintaining very high dielectric breakdown strength values. These increases are partially offset by small increases in mechanical and electrical losses. Calculations based on a simple model show that the generator energy density can be improved by a factor of 3 for a 20wt.% TiO2 loading at a strain of 50% in area. The calculated generator energy density values exceed the maximum values measured experimentally for highly prestrained VHB4910 acrylic elastomers. The focus on high energy density materials ignores the fact that not all applications require such a material, and that some applications may, in fact, benefit from the use of a softer material that is less intrusive. However, for lower energy density materials, parasitic losses due to electrode resistance and viscoelasticity play a larger role as relative energy gains are lower. With this is mind, a soft silicone single walled carbon nanotube composite is developed. The composite is very soft, has low viscoelastic losses, and is capable of being stretched up to>150% strain with only a marginal increase in resistance. The composite is also capable of being repeatedly stretched at up to 120% strain for over 1000 cycles without any appreciable change in resistance and is capable of being stretched at strain rate up to 100%/s or higher without affecting the performance of the electrode. Two applications for dielectric elastomer actuators are also explored. A pressure-based ocean wave energy harvesting concept was introduced that does not use any moving parts. A footfall energy harvester concept is also developed capable of being deployed inside the sole of a shoe or as a flexible floor tile.
Book Synopsis Fabrication, Modeling, and Control of Dielectric Elastomer Actuator by : Zhihang Ye
Download or read book Fabrication, Modeling, and Control of Dielectric Elastomer Actuator written by Zhihang Ye and published by . This book was released on 2017 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dielectric elastomer (DE) is an important kind of electro active polymer. Its softness and unique movement generating mechanism make people recognize it as artificial muscle. Existing studies focusing on it have revealed many important properties of this soft material. Fundamental researches show the working principle of how DE material can convert electrical energy and mechanical energy bi-directionally. Various actuators, devices, and robots are also developed to show the great potential of DE material in future applications. However, DE material’s nonlinear visco-elasticity and uncommon configuration in applications pose significant challenge in the developing of practical DE applications. Starting from the very basics of DE material, the working principle, modeling work, and famous applications are reviewed. Based on these fundamental knowledge of DE material, fabrications of two types of DE actuators are attempted, which demonstrate and verify the promising usage of DE material in future’s soft actuator and robotic applications. DE material’s movement generating mechanism also gives the capability of self-sensing. Software methods, including polynomial fitting and artificial neural network, are used to realize the self-sensing function in DE actuator. Different applications of DE actuators are attempted. A DE diaphragm actuator for human pulse tracking purpose is designed, fabricated, and tested. Experimental results show it can convert human pulse data into compliant vibration with good accuracy, which shows it has great potential in future’s medical applications. By patterning the diaphragm actuator’s electrode, a new type of 2-DoF maneuverable lase manipulator is created. The manipulator is capable of tracking 2-DoF angular reference with soft and gearless structure. It is expected that this new type laser manipulator can be used in laser servo system under special environment.
Book Synopsis Development of Integrated Dielectric Elastomer Actuators (IDEAS) by : Alexander K. Price
Download or read book Development of Integrated Dielectric Elastomer Actuators (IDEAS) written by Alexander K. Price and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: During the last five years, great advancements in microfluidics have been achieved with the development of "sample-in-answer-out" systems. Such systems have begun to realize the true potential of analytical miniaturization since the concept of the "micro-Total Analysis System" was first envisioned. These systems are characterized by the elegant integration of multiple fluid-handling channel architectures that enable serial execution of sample preparation, separation and detection techniques on a single device. While miniaturization and portability are often identified as key advantages for microfluidics, these highly integrated systems are heavily reliant upon large off-chip equipment, i.e. the microchip is often tethered to the laboratory via multiple syringe pumps, vacuum pumps, solenoid valves, gas cylinders and high voltage power supplies. In this dissertation, a procedure for the facile integration of dielectric elastomer (DE) actuators (called IDEAs) onto microfluidic devices is described. Poly(dimethylsiloxane) (PDMS) is commonly used as a microchip substrate because it is cheap and easy to fabricate, mechanically robust and optically transparent. The operation of an IDEA exploits the ability of PDMS to behave as a smart material and deform in the presence of an electric field. In Chapter 2, the fabrication of IDEA units on a standard microchip electrophoresis device is described. IDEA-derived injections were used to evaluate the physical performance of this novel actuator configuration. In Chapter 3, the analytical merits of IDEA-derived injections were evaluated. Sampling bias caused by electokinetic injection techniques has been problematic for conventional microchip electrophoresis systems due to the lack of fluid access. The hydrodynamic injections created by IDEA operation were found to be highly reproducible, efficient, and possess a negligible degree of sampling bias. In Chapter 4, the spatial characteristics of microchannel deformation due to IDEA actuation have been investigated using fluorescence microscopy. It was determined that the DE compresses more along the edge of the channel than in the middle of the channel. This information can be used to design a new generation of more efficient IDEAs.
Book Synopsis Dielectric Elastomers for Fluidic and Biomedical Applications by : David McCoul
Download or read book Dielectric Elastomers for Fluidic and Biomedical Applications written by David McCoul and published by . This book was released on 2015 with total page 379 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dielectric elastomers have demonstrated tremendous potential as high-strain electromechanical transducers for a myriad of novel applications across all engineering disciplines. Because their soft, viscoelastic mechanical properties are similar to those of living tissues, dielectric elastomers have garnered a strong foothold in a plethora of biomedical and biomimetic applications. Dielectric elastomers consist of a sheet of stretched rubber, or elastomer, coated on both sides with compliant electrode materials; application of a voltage generates an electrostatic pressure that deforms the elastomer. They can function as soft generators, sensors, or actuators, and this last function is the focus of this dissertation. Many design configurations are possible, such as stacks, minimum energy structures, interpenetrating polymer networks, shape memory dielectric elastomers, and others; dielectric elastomers are already being applied to many fields of biomedicine. The first part of the original research presented in this dissertation details a PDMS microfluidic system paired with a dielectric elastomer stack actuator of anisotropically prestrained VHB(TM) 4910 (3M(TM)) and single-walled carbon nanotubes. These electroactive microfluidic devices demonstrated active increases in microchannel width when 3 and 4 kV were applied. Fluorescence microscopy also indicated an accompanying increase in channel depth with actuation. The cross-sectional area strains at 3 and 4 kV were approximately 2.9% and 7.4%, respectively. The device was then interfaced with a syringe pump, and the pressure was measured upstream. Linear pressure-flow plots were developed, which showed decreasing fluidic resistance with actuation, from 0.192 psi/(microL/min) at 0 kV, to 0.160 and 0.157 psi/(microL/min) at 3 and 4 kV, respectively. This corresponds to an ~18% drop in fluidic resistance at 4 kV. Active de-clogging was tested in situ with the device by introducing ~50 m diameter PDMS microbeads and other smaller particulate debris into the system. After a channel blockage was confirmed, three actuation attempts successfully cleared the blockage. Further tests indicated that the device were biocompatible with HeLa cells at 3 kV. To our knowledge this is the first pairing of dielectric elastomers with microfluidics in a non-electroosmotic context. Applications may include adaptive microfilters, micro-peristaltic pumps, and reduced-complexity lab-on-a-chip devices. Dielectric elastomers can also be adapted to manipulate fluidic systems on a larger scale. The second part of the dissertation research reports a novel low-profile, biomimetic dielectric elastomer tubular actuator capable of actively controlling hydraulic flow. The tubular actuator has been established as a reliable tunable valve, pinching a secondary silicone tube completely shut in the absence of a fluidic pressure bias or voltage, offering a high degree of resistance against fluidic flow, and able to open and completely remove this resistance to flow with an applied low power actuation voltage. The system demonstrates a rise in pressure of ~3.0 kPa when the dielectric elastomer valve is in the passive, unactuated state, and there is a quadratic fall in this pressure with increasing actuation voltage, until ~0 kPa is reached at 2.4 kV. The device is reliable for at least 2,000 actuation cycles for voltages at or below 2.2 kV. Furthermore, modeling of the actuator and fluidic system yields results consistent with the observed experimental dependence of intrasystem pressure on input flow rate, actuator prestretch, and actuation voltage. To our knowledge, this is the first actuator of its type that can control fluid flow by directly actuating the walls of a tube. Potential applications may include an implantable artificial sphincter, part of a peristaltic pump, or a computerized valve for fluidic or pneumatic control. The final part of the dissertation presents a novel dielectric elastomer band with integrated rigid elements for the treatment of chronic acid reflux disorders. This dielectric elastomer ring actuator consists of a two-layer stack of prestretched VHB(TM) 4905 with SWCNT electrodes. Its transverse prestretch was maintained by selective rigidification of the VHB(TM) using a UV-curable, solution-processable polymer network. The actuator exhibited a maximum vertical (circumferential) actuation strain of 25% at 3.4 kV in an 24.5 g weighted isotonic setup. It also exhibited the required passive force of 0.25 N and showed a maximum force drop of 0.11 N at 3.32 kV during isometric tests at 4.5 cm. Modeling was performed to determine the prestretches necessary to achieve maximum strain while simultaneously exerting the force of 0.25 N, which corresponds to a required pinching pressure of 3.35 kPa. Modeling also determined the spacing between and number of rigid elements required. The theoretical model curves were adjusted to account for the passive rigid elements, as well as for the addition of margins; the resulting plots agrees well with experiment. The performance of the DE band is comparable to that of living muscle, and this is the first application of dielectric elastomer actuators in the design of a medical implant for the treatment of gastrointestinal disorders. Related applications that could result from this technology are very low-profile linear peristaltic pumps, artificial intestines, an artificial urethra, and artificial blood vessels.
