20 Extending Applications of Dielectric Elastomer Artificial Muscles to Wireless Communication Systems (original) (raw)
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Dielectric elastomer artificial muscle actuators: Toward biomimetic motion
2002
To achieve desirable biomimetic motion, actuators must be able to reproduce the important features of natural muscle such as power, stress, strain, speed of response, efficiency, and controllability. It is a mistake, however, to consider muscle as only an energy output device. Muscle is multifunctional. In locomotion, muscle often acts as an energy absorber, variable-stiffness suspension element, or position sensor, for example. Electroactive polymer technologies based on the electric-field-induced deformation of polymer dielectrics with compliant electrodes are particularly promising because they have demonstrated high strains and energy densities. Testing with experimental biological techniques and apparatus has confirmed that these "dielectric elastomer" artificial muscles can indeed reproduce several of the important characteristics of natural muscle. Several different artificial muscle actuator configurations have been tested, including flat actuators and tubular rolls. Rolls have been shown to act as structural elements and to incorporate position sensing. Biomimetic robot applications have been explored that exploit the muscle-like capabilities of the dielectric elastomer actuators, including serpentine manipulators, insect-like flappingwing mechanisms, and insect-like walking robots.
Dielectric elastomers as next-generation polymeric actuators
Soft Matter, 2007
Due to their versatile properties, robust behavior, facile processability and low cost, organic polymers have become the material of choice for an increasing number of mature and cutting-edge technologies. In the last decade or so, a new class of polymers capable of responding to external electrical stimulation by displaying significant size or shape change has emerged. These responsive materials, collectively referred to as electroactive polymers (EAPs), are broadly classified as electronic or ionic according to their operational mechanism. Electronic EAPs generally exhibit superior performance relative to ionic EAPs in terms of actuation strain, reliability, durability and response time. Among electronic EAPs, dielectric elastomers exhibit the most promising properties that mimic natural muscle for use in advanced robotics and smart prosthetics, as well as in haptic and microfluidic devices. Elastomers derived from homopolymers such as acrylics and silicones have received considerable attention as dielectric EAPs, whereas novel dielectric EAPs based on selectively swollen nanostructured block copolymers with composition-tailorable properties have only recently been reported. Here, we provide an overview of various EAPs in terms of their operational mechanisms, uses and shortcomings, as well as a detailed account of dielectric elastomers as next-generation actuators.
Muscle-like actuators? A comparison between three electroactive polymers
2001
Muscles fulfill several functions within an animal's body. During locomotion they propel and control the limbs in unstructured environments. Therefore, the functional workspace of muscle needs to be represented by variables describing energy management (i.e. power output, efficiency) as well as control aspects (i.e. stiffness, damping). Muscles in the animal kingdom vary greatly with respect to those variables. To study if ElectroActive Polymer's (EAP) can be considered as artificial muscles we are making a direct comparison between the contractile properties of EAP's and biological muscle. We have measured the functional workspace of EAP actuators using the same setup and techniques that we use to test biological muscle. We evaluated the properties of three different EAP materials; the acrylic and silicone dielectric elastomers developed at 'SRI International' and the high-energy electron-irradiated co-polymers (P(VDF-TrFE)) developed at the MRL laboratory at Penn State University. Initial results indicate that the EAP materials partly capture the functional workspace of natural muscle and sometimes even exceed the capabilities of muscle. Based on the data we have collected it seems that both EAP technologies have characteristics that could qualify them as artificial muscles.
Electroactive polymers (EAP) low-mass muscle actuators
Smart Structures and Materials 1997: Smart Structures and Integrated Systems, 1997
Actuation devices are used for many space applications with an increasing need to reduce their size, mass, and power consumption as well as cut their cost. Existing transducing actuators, such as piezoceramics, induce limited displacement levels.
Electroactive Polymer Artificial Muscle
Journal of the Robotics Society of Japan, 2006
biologically inspired hexapedal robot using field-effect electroactive elastomer artificial muscles,•h Proc. SPIE 8th Annual Symposium on Smart Structures and Materials 2001: Industrial and Commercial Applications of Smart Structures Technologies, vol.4332, 2001.
Low-mass muscle actuators using electroactive polymers (EAP
1998
NASA is seeking to reduce the mass, size, consumed power, and cost of the instrumentation used in its future missions. An important element of many instruments and devices is the actuation mechanism and electroactive polymers offer an effective alternative to current actuators. In this study, two families of electroactive polymer materials were investigated, including bending ionomers and longitudinal electrostatically driven elastomers. These materials were demonstrated to effectively actuate manipulation devices and their performance is being enhanced in this on-going study. The recent observations are reported in this paper, which also include cryovac tests at conditions that simulate Mars environment. Tests at T equals -140 degree(s)C and P approximately 1 Torr, which are below Mars conditions, showed that the bending actuator was still responding with a measurable actuation displacement. Analysis of the electrical characteristics of the ionomer showed that it is a current driven material rather than voltage driven. Measurements of transient currents in response to a voltage step shows a time constant on the order of few seconds with a response speed that is enhanced with the decrease in drive voltage. The ionomer main limitation is its requirement for being continuously moist. Tests showed that while the performance degrades as the material becomes dry, its AC impedance increases, reaching an order of magnitude higher than the wet ionomer. This response provides a gauging indication of the material wetness status. Methods of forming the equivalent of a skin to protect the moisture content of the ionomer are being sought and a limited success was observed using thick platinum electroding as well as when using polymeric coating.
Multi-functional dielectric elastomer artificial muscles for soft and smart machines
Journal of Applied Physics, 2012
Dielectric elastomer (DE) actuators are popularly referred to as artificial muscles because their impressive actuation strain and speed, low density, compliant nature, and silent operation capture many of the desirable physical properties of muscle. Unlike conventional robots and machines, whose mechanisms and drive systems rapidly become very complex as the number of degrees of freedom increases, groups of DE artificial muscles have the potential to generate rich motions combining many translational and rotational degrees of freedom. These artificial muscle systems can mimic the agonist-antagonist approach found in nature, so that active expansion of one artificial muscle is taken up by passive contraction in the other. They can also vary their stiffness. In addition, they have the ability to produce electricity from movement. But departing from the high stiffness paradigm of electromagnetic motors and gearboxes leads to new control challenges, and for soft machines to be truly dexterous like their biological analogues, they need precise control. Humans control their limbs using sensory feedback from strain sensitive cells embedded in muscle. In DE actuators, deformation is inextricably linked to changes in electrical parameters that include capacitance and resistance, so the state of strain can be inferred by sensing these changes, enabling the closed loop control that is critical for a soft machine. But the increased information processing required for a soft machine can impose a substantial burden on a central controller. The natural solution is to distribute control within the mechanism itself. The octopus arm is an example of a soft actuator with a virtually infinite number of degrees of freedom (DOF). The arm utilizes neural ganglia to process sensory data at the local "arm" level and perform complex tasks. Recent advances in soft electronics such as the piezoresistive dielectric elastomer switch (DES) have the potential to be fully integrated with actuators and sensors. With the DE switch, we can produce logic gates, oscillators, and a memory element, the building blocks for a soft computer, thus bringing us closer to emulating smart living structures like the octopus arm. The goal of future research is to develop fully soft machines that exploit smart actuation networks to gain capabilities formerly reserved to nature, and open new vistas in mechanical engineering. V
Smart Dielectric Elastomers and Their Potential for Biodevices
2008
Dielectric Elastomer (DE) actuators are compliant, ultra lightweight electromechanical devices that can be used as actuators, sensors, and power generators. While a relatively new technology, DE actuators can be produced using biocompatible materials and have already exhibited excellent performance in terms of strain, speed, pressure, specific energy density, and efficiency when compared to conventional actuation technologies and natural muscle. Further research is required in order for promising laboratory results to be translated into real-world applications, particularly in the areas of modelling and control, but the potential for multiple functions to be integrated into a single element is an exciting prospect for flexible smart structures and biodevices. 2 DIELECTRIC ELASTOMER OPERATING PRINCIPLE 2.1 Basic DE Structure A DE actuator is a compliant capacitor consisting of an incompressible soft polymer membrane dielectric with compliant electrodes applied on both sides. When used as an actuator, the charge accumulated on the electrodes when a voltage is 285
2011
The focus of this project is to see if it is possible to integrate multiple EAP materials in an electro-mechanical system to produce a closer representation of a biological muscle with smooth varying motion. In this preliminary study, two common types of EAPs, ionic and dielectric, were investigated to determine their mechanical and electrical properties in order to assess their potential to be combined into a working artificial electromechanical muscle prototype at a later time. A conceptual design for an artificial electromechanical muscle was created with biomimetic relationships between EAP materials and the human bicep muscle. With the assistance of the Rochester General Hospital, a human arm model, isolating the bicep muscle, was created to calculate mechanical characteristics of the bicep brachii. From the human arm model, bicep muscle characteristics were compared to those of the dielectric EAP because of the ability for the EAP to output relatively high force and strain during actuation. It was found that the current state of the art of EAPs is a long way from making this a reality due to their limiting force output and voltage requirements. The feasibility of developing an artificial electromechanical muscle with EAP actuators is not possible with current technology.