Modelling of Multilayer Perforated Electrodes for Dielectric Elastomer Actuator Applications

AbstractDielectric elastomer actuators (DEAs), which are inherently complaint capacitors, are emerging as pseudo-muscular actuators with a wide range of applications. In order to achieve high stretchability for large DEA actuation, carbon nanotube (CNT) and other 1D materials-based electrodes are used to maintain conductance at large strains. These electrodes are typically fabricated using spray coating or filter transfer method and resemble a perforated electrode under high magnification. Hence, there can be a loss of field and stray capacitance when multiple layers of carbon nanotubes (CNTs)-based electrodes are used. This study investigates the effect of microscopic perforations on the nature of electric fields and on the capacitance of multi-layered CNT-based DEA structures with various dimensions and geometric properties of the electrodes. It has been found that the capacitance decreases with increase in the perforations however its effect is limited for a reasonable coverage. The change in normalized is found to be negligible (∼5%) for an electrode coverage area of over 90%, however, the maximum output work reduces by 18.2%. This analysis is important to develop robust and reliable CNT-based DEA structures, without using excessive CNTs which can lead to increased mechanical stiffness of the electrodes.

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Nonlinear Dynamics of a Dielectric Elastomer Membrane Under Compressive Loading

Volume 12: Mechanics of Solids, Structures, and Fluids ◽

10.1115/imece2020-24275 ◽

2020 ◽

Author(s):

Robert L. Lowe ◽

Christopher G. Cooley

Keyword(s):

Nonlinear Dynamics ◽

Dynamic Response ◽

Frequency Response ◽

Compressive Loading ◽

Excitation Frequency ◽

Harmonic Excitation ◽

Dielectric Elastomer ◽

Large Strains ◽

Membrane Stretch ◽

Wide Range

Abstract This paper investigates the nonlinear dynamics of square dielectric elastomer membranes under time-dependent, through-thickness compressive loading. The dielectric elastomer is modeled as an isotropic ideal dielectric, with mechanical stiffening at large strains captured using the Gent hyperelastic constitutive model. The equation of motion for the in-plane membrane stretch is derived using Hamilton’s principle. The static response of the membrane is first investigated, with equilibrium stretches calculated numerically for a wide range of compressive pre-loads and applied voltages. Snap-through instabilities are observed, with the critical snap-through voltage decreasing with increasing compressive pre-load. The dynamic response of the membrane is then investigated under forced harmonic excitation. Frequency response plots characterizing the steady-state vibration reveal primary, subharmonic, and superharmonic resonances. Near these resonances, two stable vibration states are possible, corresponding to upper and lower branches in the frequency response. Significant and practically meaningful differences in the dynamic response are observed when the system vibrates at a fixed frequency about the upper and lower branches, a feature not discussed in previous research.

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A broadbanded pressure differential wave energy converter based on dielectric elastomer generators

Nonlinear Dynamics ◽

10.1007/s11071-021-06721-8 ◽

2021 ◽

Author(s):

Michele Righi ◽

Giacomo Moretti ◽

David Forehand ◽

Lorenzo Agostini ◽

Rocco Vertechy ◽

...

Keyword(s):

Wave Energy ◽

Large Deformations ◽

Dielectric Elastomer ◽

Wave Energy Converter ◽

Pressure Differential ◽

Design Stage ◽

Small Scale ◽

Energy Converter ◽

Wide Range ◽

The Waves

AbstractDielectric elastomer generators (DEGs) are a promising option for the implementation of affordable and reliable sea wave energy converters (WECs), as they show considerable promise in replacing expensive and inefficient power take-off systems with cheap direct-drive generators. This paper introduces a concept of a pressure differential wave energy converter, equipped with a DEG power take-off operating in direct contact with sea water. The device consists of a closed submerged air chamber, with a fluid-directing duct and a deformable DEG power take-off mounted on its top surface. The DEG is cyclically deformed by wave-induced pressure, thus acting both as the power take-off and as a deformable interface with the waves. This layout allows the partial balancing of the stiffness due to the DEG’s elasticity with the negative hydrostatic stiffness contribution associated with the displacement of the water column on top of the DEG. This feature makes it possible to design devices in which the DEG exhibits large deformations over a wide range of excitation frequencies, potentially achieving large power capture in a wide range of sea states. We propose a modelling approach for the system that relies on potential-flow theory and electroelasticity theory. This model makes it possible to predict the system dynamic response in different operational conditions and it is computationally efficient to perform iterative and repeated simulations, which are required at the design stage of a new WEC. We performed tests on a small-scale prototype in a wave tank with the aim of investigating the fluid–structure interaction between the DEG membrane and the waves in dynamical conditions and validating the numerical model. The experimental results proved that the device exhibits large deformations of the DEG power take-off over a broad range of monochromatic and panchromatic sea states. The proposed model demonstrates good agreement with the experimental data, hence proving its suitability and effectiveness as a design and prediction tool.

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The vibration of electrified water drops

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1971.0082 ◽

1971 ◽

Vol 322 (1551) ◽

pp. 523-534 ◽

Cited By ~ 20

Keyword(s):

Electric Field ◽

Electric Fields ◽

Axial Ratio ◽

Uniform Electric Field ◽

Interferometric Technique ◽

Photographic Analysis ◽

Wide Range ◽

Water Drops ◽

Strength And Deformation ◽

A Charge

Pressure has been used as the principal parameter in calculations of the fundamental vibrational frequencies of spherical drops of radius R , density ρ, and surface tension T carrying a charge Q or uncharged spheroidal drops of axial ratio a / b situated in a uniform electric field of strength E . Freely vibrating charged drops have a frequency f = f 0 ( 1 - Q 2 /16π R 3 T ) ½ , as shown previously by Rayleigh (1882) using energy considerations; f 0 is the vibrational frequency of non-electrified drops (Rayleigh 1879). The fundamental frequency of an uncharged drop in an electric field will decrease with increasing field strength and deformation a / b and will equal zero when E ( R )/ T ) ½ = 1.625 and a / b = 1.86; these critical values correspond to the disintegration conditions derived by Taylor (1964). An interferometric technique involving a laser confirmed the accuracy of the calculations concerned with charged drops. The vibration of water drops of radius around 2 mm was studied over a wide range of temperatures as they fell through electric fields either by suspending them in a vertical wind tunnel or allowing them to fall between a pair of vertical electrodes. Photographic analysis of the vibrations revealed good agreement between theory and experiment over the entire range of conditions studied even though the larger drops were not accurately spheroidal and the amplitude of the vibrations was large.

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Designing Soft Reactive Adhesives by Controlling Polymer Chemistry

MRS Bulletin ◽

10.1557/mrs2003.122 ◽

2003 ◽

Vol 28 (6) ◽

pp. 424-427 ◽

Cited By ~ 3

Author(s):

Agnès Aymonier ◽

Eric Papon

Keyword(s):

Automotive Industry ◽

Ease Of Use ◽

Large Strains ◽

Structural Adhesives ◽

Wide Range ◽

Step Growth ◽

Visible Irradiation ◽

Step Growth Polymerization ◽

Uv Visible ◽

Activation Heat

AbstractSoft reactive adhesives (SRAs) are polymer-based materials (e.g., polyurethanes, polysiloxanes, polydienes) designed to be further vulcanized or slightly cross-linked through external activation (heat, moisture, oxygen, UV–visible irradiation, etc.), either at the time of their application or within a subsequent predefined period. They are used mainly as mastics, or sealing compounds, in a wide range of industrial and commercial fields such as construction, footwear, and the automotive industry. Generally deposited as thick films, SRAs behave as structural adhesives; their low elastic moduli accommodate large strains between the bonded parts without incurring permanent damage. Other outstanding attributes of SRAs are their resistance to solvents, their ability to withstand aggressive environments, and their ease of use. This article discusses examples of SRAs and, more specifically, shows how the cross-linking chemistry, mainly through step-growth polymerization, provides their primary advantages.

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Thermal Response of a Viscoelastic Rod Under Cyclic Loading

Journal of Applied Mechanics ◽

10.1115/1.3423232 ◽

1974 ◽

Vol 41 (1) ◽

pp. 229-233 ◽

Cited By ~ 7

Author(s):

S. Mukherjee

Keyword(s):

Cyclic Loading ◽

Thermal Response ◽

Time History ◽

Thermomechanical Coupling ◽

Large Strains ◽

Driving Frequency ◽

Wide Range ◽

History Of ◽

Complex Young’S Modulus ◽

Viscoelastic Rod

Thermal response of a viscoelastic rod under cyclic loading is discussed by determining the stresses and temperature in a viscoelastic rod insulated on its lateral surface and driven by a sinusoidal stress at one end. Temperature dependence of the complex Young’s modulus of the rod and the effect of thermomechanical coupling are included in the analysis. A method of finite differences is used to directly determine the steady-state stresses and temperature without obtaining the complete time history of the process. The iterative algorithm used is very efficient and converges rapidly for a wide range of driving stress amplitudes and frequencies. It is found that rapid rise of temperature to dangerous levels occurs for relatively low values of driving stress amplitudes, especially if the driving frequency is close to one of the critical frequencies of the rod. Drastic softening of the rod leads to large strains. Thus failure of the rod could occur at low values of the driving stress.

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Improving of electrical channels for magnetotelluric sounding instrumentation

Geoscientific Instrumentation Methods and Data Systems ◽

10.5194/gi-4-149-2015 ◽

2015 ◽

Vol 4 (2) ◽

pp. 149-154 ◽

Cited By ~ 1

Author(s):

A. M. Prystai ◽

V. O. Pronenko

Keyword(s):

Electric Field ◽

Electric Fields ◽

Deep Structure ◽

Experimental Tests ◽

Magnetotelluric Sounding ◽

Earth’S Crust ◽

Geomagnetic Variations ◽

The Earth ◽

Wide Range ◽

Earth's Crust

Abstract. The study of the deep structure of the Earth's crust is of great interest for both applied (e.g. mineral exploration) and scientific research. For this the electromagnetic (EM) studies which enable one to construct the distribution of electrical conductivity in the Earth's crust are of great use. The most common method of EM exploration is magnetotelluric sounding (MT). This passive method of research uses a wide range of natural geomagnetic variations as a powerful source of electromagnetic induction in the Earth, producing telluric current variations there. It includes the measurements of variations of natural electric and magnetic fields in orthogonal directions at the surface of the Earth. By this, the measurements of electric fields are much more complicated metrological processes, and, namely, they limit the precision of MT prospecting. This is especially complicated at deep sounding when measurements of long periods are of interest. The increase in the accuracy of the electric field measurement can significantly improve the quality of MT data. Because of this, the development of a new version of an instrument for the measurements of electric fields at MT – both electric field sensors and the electrometer – with higher levels relative to the known instrument parameter level – was initiated. The paper deals with the peculiarities of this development and the results of experimental tests of the new sensors and electrometers included as a unit in the long-period magnetotelluric station LEMI-420 are given.

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Orientation of Temporal Interference for Non-Invasive Deep Brain Stimulation in Epilepsy

10.1101/2020.07.07.191692 ◽

2020 ◽

Author(s):

Florian Missey ◽

Evgeniia Rusina ◽

Emma Acerbo ◽

Boris Botzanowski ◽

Romain Carron ◽

...

Keyword(s):

Electric Fields ◽

Brain Regions ◽

Intracranial Stimulation ◽

Epileptogenic Zone ◽

Implanted Electrodes ◽

Non Invasive ◽

Gamma Range ◽

Wide Range ◽

Drug Resistant Epilepsy ◽

Intracranial Electrodes

AbstractIn patients with focal drug-resistant epilepsy, electrical stimulation from intracranial electrodes is frequently used for the localization of seizure onset zones and related pathological networks. The ability of electrically stimulated tissue to generate beta and gamma range oscillations, called rapid-discharges, is a frequent indication of an epileptogenic zone. However, a limit of intracranial stimulation is the fixed physical location and number of implanted electrodes, leaving numerous clinically and functionally relevant brain regions unexplored. Here, we demonstrate an alternative technique relying exclusively on nonpenetrating surface electrodes, namely an orientation-tunable form of temporally-interfering (TI) electric fields to target the CA3 of the mouse hippocampus which focally evokes seizure-like events (SLEs) having the characteristic frequencies of rapid-discharges, but without the necessity of the implanted electrodes. The orientation of the topical electrodes with respect to the orientation of the hippocampus is demonstrated to strongly control the threshold for evoking SLEs. Additionally, we demonstrate the use of square waves as an alternative to sine waves for TI stimulation. An orientation-dependent analysis of classic implanted electrodes to evoke SLEs in the hippocampus is subsequently utilized to support the results of the minimally-invasive temporally-interfering fields. The principles of orientation-tunable TI stimulation seen here can be generally applicable in a wide range of other excitable tissues and brain regions, overcoming several limitations of fixed electrodes which penetrate tissue.

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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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A III B VI PHOTOVOLTAIC RECEPTORS FOR EXPERIMENTAL DETERMINATION OF CARBON COMPOUNDS IN ATMOSPHERE

Journal of Engineering Studies and Research ◽

10.29081/jesr.v19i3.111 ◽

2016 ◽

Vol 19 (3) ◽

Author(s):

IULIANA CARAMAN ◽

IGOR EVTODIEV ◽

OXANA RACOVEŢ ◽

MARIUS STAMATE

Keyword(s):

Electric Fields ◽

Full Range ◽

Absorption Bands ◽

Gaseous State ◽

Wide Range ◽

Carbon Compounds ◽

Strong Electric Fields ◽

Qualitative Measurements ◽

Semiconductor Type

This paper examines the prospects of using semiconductor layered A III B VI type - photovoltaic cells and the photoresistors as receptors for quantitative and qualitative measurements of carbon oxides. Carbon compounds in gaseous state form absorption bands of electromagnetic radiation in a wide range of spectrum (200 ÷ 100 000) cm-1. The light absorbed or emitted in these bands at the excitations with ionizing radiation (X, γ) or strong electric fields contain direct information about the concentration of these molecules. The frequencies that correspond to maxima of these bands are characteristic parameters of absorbing molecules. Fundamental absorption bands of CO, CO 2 and NC have the edge of band at the border of ultraviolet-vacuum, while the emission bands d cover their full range of wave numbers from 45000 cm-1 to 10000 cm-1. Two types of radiation receptors from lamellar semiconductor type AIIIBVI photosensitive in this spectral range are studied.

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