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Flexible hybrid electronic (FHE) materials and devices exploit the interaction of mechanical and electromagnetic properties to operate in new form factors and loading environments, which are key for advancing wearable sensors, flexible antennas, and soft robotic skin technologies. Dielectric elastomer (DE) architectures offer a novel substrate material for this application space as they are a class of strain‐tolerant and programmable metamaterials that derive their mechanical and dielectric properties from their architecture. Due to their hyperelasticity, dielectric elastomers can leverage reversible finite deformation to physically reconfigure their internal architecture to repeatedly tune their material behavior. Here a combined computational and experimental study of two dielectric elastomer architectures, based on square and hexagonal unit cell periodicities are presented. A shift in effective permittivity is observed due to the relative increase in matrix volume and the rearrangement of the electric field distribution in the cells. Additive fabrication allows rapid unit cell geometry customization for tuning the electromechanical response of the architectures. Effective permittivity shifts Δε2 > 0.7 under compressive strains of 35% are observed. The practical utility of this strain‐tunable permittivity is demonstrated in a microstrip patch antenna, which exhibits shifts in resonance frequency greater than 110 MHz when the dielectric elastomer substrate is compressed. [ABSTRACT FROM AUTHOR]

This paper presents a method to achieve high deformability levels in dielectric elastomer actuators (DEAs) by applying a modulated voltage waveform. The method relies on supplying the electrostatic energy during the specific phase of the oscillation cycle, resulting in the enhanced travel range at a relatively low driving voltage. We consider a standard sandwich configuration of the DE actuator with neo-Hookean material model and outline an energy-based approach for delineating the underlying principles of the proposed method. A comparison of the deformability levels achieved using the quasi-static, Heaviside step, and the modulated input waveforms is presented. Significant reduction in instability voltages together with a considerable increase in the stable actuation limit is observed in the case of the modulated voltage input. The estimates of the stability thresholds are validated by integrating the equation of motion obtained using Hamilton's principle. The effect of energy dissipation is assessed by considering variations in the quality factor. Further, a qualitative comparison with experimental observations is presented highlighting the practical feasibility of the method. This investigation can find its potential use in the design and development of DEAs subjected to a time-dependent motion. [ABSTRACT FROM AUTHOR]

This paper reports an energy-based method for the dynamic pull-in instability analysis of a spherical dielectric elastomer (DE) balloon subjected to a quasistatically applied inflation pressure and a Heaviside step voltage across the balloon wall. The proposed technique relies on establishing the energy balance at the point of maximum stretch in an oscillation cycle, followed by the imposition of an instability condition for extracting the threshold parameters. The material models of the Ogden family are employed for describing the hyperelasticity of the balloon. The accuracy of the critical dynamic pull-in parameters is established by examining the saddle-node bifurcation in the transient response of the balloon obtained by integrating numerically the equation of motion, derived using the Euler-Lagrange equation. The parametric study brings out the effect of inflation pressure on the onset of the pull-in instability in the DE balloon. A quantitative comparison between the static and dynamic pull-in parameters at four different levels of the inflation pressure is presented. The results indicate that the dynamic pull-in instability gets triggered at electric fields that are lower than those corresponding to the static instability. The results of the present investigation can find potential use in the design and development of the balloon actuators subjected to transient loading. The method developed is versatile and can be used in the dynamic instability analysis of other conservative systems of interest. [ABSTRACT FROM AUTHOR]

Magnetorheological elastomers (MRE) can change their shape and properties when activated by an external magnetic field. The attractive tunable properties of this stimuli-responsive composite can be further amplified by utilizing the magneto-mechanical instability phenomenon, frequently leading to dramatic microstructure transformation. In this work, we investigate the buckling behavior of the composite system consisting of a magnetoactive layer embedded into an inactive elastomeric matrix. The composite is subjected to compressive strains in the presence of a high magnetic field. Our experimental results show that the critical buckling strain is highly tunable by the applied magnetic field. In particular, the composite buckles significantly earlier when the field is applied, leading to well-developed controllable wavy patterns in the post-buckling regime. To elucidate the mechanisms associated with the experimentally observed magneto-mechanical instability, we investigated the stability using numerical analysis. The developed computational model utilizes our new experimental data on the mechanical and magnetic properties of the composite (including magnetization and the magnetic susceptibility of the MRE composite as a function of the volume fraction of magnetic particles). The numerical model is verified against the experimental results, showing its capability to predict the onset of the magneto-mechanical instability and the post-buckling behavior of the MRE. Collectively, the study demonstrates MRE instability tuning in a laminate form factor and outlines the strategy and benefits of harnessing two field physics for controlling bifurcations. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the stability of microstructured dielectric elastomer (DE) plates under electro-mechanical finite deformations. We examine the influence of the DE composite microstructure parameters on the stability of the DE composite plate. In particular, we analyze the DE plates made out of laminated ideal dielectric phases. We use an exact solution for the incompressible DE laminates to determine the effective material behavior of the composite plates. The corresponding micromechanics-based energy density functions are used in the subsequent analysis of the DE plate stability. The unstable domains for different materials compositions, volume fractions, and properties of the DE composite phases are determined. Finally, we compare these results for the onset of structural instabilities in DE plates with the material instabilities predicted based on the loss of ellipticity analysis. • The stability of microstructured DE laminated plates is examined. • The influence of material compositions are determinedStructural (plate) and microstructural (or material) instabilities in DE plates are compared. [ABSTRACT FROM AUTHOR]

• The interplay between the material composition and deformation-induced effective permittivity in dielectric elastomer (DE) composites is studied. • DE composites with periodic microstructures of (a) circular and (b) elliptical inclusions, (c) pair of inclusions, and (d) randomly distributed inclusions with varying number of the particles in the unit cell, and periodic porous composites are analyzed. • An explicit relation between the effective permittivity and stretch is derived. • The permittivity tunability in DE periodic porous composites structures experiencing elastic instabilities is realized numerically. We study the interplay between the material composition and deformation in dielectric elastomer (DE) composites with periodically and randomly distributed particles embedded in a soft matrix. We focus on the deformation-induced tunability of the effective permittivity in DE composites. We examine the effects of microstructural periodicity and its transition towards random distribution. In particular, we analyze the DE composites with periodic microstructures of (a) circular and (b) elliptical inclusions, (c) pair of inclusions, and (d) randomly distributed inclusions with different numbers of the particles in the unit cell. The finitely deformed DE composites with ideal dielectric elastomer constituents are analyzed numerically. In addition, for the periodic DE composites with circular inclusions, we derive an explicit relation between the effective permittivity and stretch. The effective permittivity of DE composites with periodic microstructures changes with deformation, whereas in DE composites with randomly distributed inclusions, the permittivity is barely affected by deformation. For the latter case, the effective permittivity attains a certain value as the number of particles in the periodic cell increases. To provide the insights on the composite behavior, a two-particle periodic system is examined. The permittivity is found to be sensitive to the orientation of the pairs with respect to the applied electric field, and the distance between the particles. The geometrical effects amplify significantly as the inter-particle distance becomes less than their two diameters. Finally, we illustrate the permittivity tunability in DE periodic porous composites structures experiencing elastic instabilities. [ABSTRACT FROM AUTHOR]