Actuation response of polyacrylate dielectric elastomers

Kofod, Guggi; Kornbluh, Roy; Pelrine, Ron; Sommer‐Larsen, Peter

doi:10.1117/12.432638

Cited by 90 publications

(98 citation statements)

References 8 publications

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“…Prestrain enhances the dielectric-breakdown field of the elastomer films. [11] Mechanistic reasons for the enhancement of dielectric strength via mechanical prestraining are not well understood; we attribute it to the increased probability of hot electrons colliding with polymer chains realigned in parallel to the film surfaces. The prestrain also realigns defects, such as fibrous impurities, non-spherical voids, and gel particles, which may be responsible for premature dielectric breakdown.…”

mentioning

confidence: 98%

Interpenetrating Polymer Networks for High‐Performance Electroelastomer Artificial Muscles

Ha¹,

Yuan²,

Pei³

et al. 2006

Advanced Materials

272

239

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Actuator materials that can reproduce the multifunctionality of natural muscles have long been desired for the development of biologically inspired robots. Electroactive polymers (EAPs) have attracted increasing attention as potential candidates for artificial muscles. While several types of EAPs have been investigated, [1][2][3][4] electroelastomers, also known as dielectric elastomers, have been particularly attractive for largestrain and high-power applications. [5][6][7] Electroelastomers based on acrylic copolymer elastomers (e.g., 3M VHB 4910) and compliant electrodes have been shown to exhibit electromechanical strains of up to 380 % in terms of area expansion. Furthermore, the specific elastic energy density (3.4 J g -1), stress (up to 8 MPa), and electromechanical conversion efficiency (60-90 %) are all extraordinarily high. However, this outstanding performance is only observed when the acrylic films are highly prestrained. The reported specific elastic-energy density and stress are calculated from the weight or volume of the active acrylic elastomers. The performance of the packaged actuators is substantially lower.A number of actuator configurations, such as bow, bowtie, rigid-frame, diaphragm, and spring-roll actuators, have been designed to support the required high prestrain. [8,9] Each of these designs has its own unique advantages for certain applications, but without exception, the prestrain-supporting structures occupy significantly more space and weigh significantly more than the films themselves. The consequence of this is that the supporting structures cause a large performance gap between the active material and the packaged actuators. In addition, the lifetimes of the actuators are limited by the concentration of stress at the interfaces between the soft polymer film and the rigid supporting structure. The shock tolerance of the actuators is also reduced because of the introduction of rigid structural components. The prestrained films exhibit stress relaxation that affects the subsequent actuation.[10]Therefore, it would be highly desirable to eliminate mechanical prestraining while still retaining its performance benefits. We report here the development of new electroelastomers that exhibit high strain without requiring high prestrain. Electrically induced strain is proportional to the square of the applied electric field. High strain necessitates high breakdown strength. Prestrain enhances the dielectric-breakdown field of the elastomer films.[11] Mechanistic reasons for the enhancement of dielectric strength via mechanical prestraining are not well understood; we attribute it to the increased probability of hot electrons colliding with polymer chains realigned in parallel to the film surfaces. The prestrain also realigns defects, such as fibrous impurities, non-spherical voids, and gel particles, which may be responsible for premature dielectric breakdown. Here, we describe new interpenetrating elastomeric networks in which the benefits resulting from prestrain are obtained without exte...

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mentioning

confidence: 98%

Interpenetrating Polymer Networks for High‐Performance Electroelastomer Artificial Muscles

Ha¹,

Yuan²,

Pei³

et al. 2006

Advanced Materials

272

239

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“…The relative permittivity is considered as a constant neglecting the electrostrictive effect of the polymer as shown by Kofod et al [24]. Our microactuator consists of a 30 μm thick PDMS membrane with a 100 μm wide compliant microelectrode on one side and a blanket compliant electrode on the other side as schematically shown in figure 1.…”

Section: Actuation Principlementioning

confidence: 99%

Microfabrication and characterization of an array of dielectric elastomer actuators generating uniaxial strain to stretch individual cells

Akbari¹,

Shea²

2012

J. Micromech. Microeng.

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Cells regulate their behavior in response to mechanical strains. Cell cultures to study mechanotransuction are typically cm 2 in area, far too large to monitor single cell response. We have developed an array of dielectric elastomer microactuators as a tool to study mechanotransduction of individual cells. The array consists of 72 100 μm × 200 μm electroactive polymer actuators which expand uniaxially when a voltage is applied. Single cells will be attached on each actuator to study their response to periodic mechanical strains. The device is fabricated by patterning compliant microelectrodes on both sides of a 30 μm thick polydimethylsiloxane membrane, which is bonded to a Pyrex chip with 200 μm wide trenches. Low-energy metal ion implantation is used to make stretchable electrodes and we demonstrate here the successful miniaturization of such ion-implanted electrodes. The top electrode covers the full membrane area, while the bottom electrodes are 100 μm wide parallel lines, perpendicular to the trenches. Applying a voltage between the top and bottom electrodes leads to uniaxial expansion of the membrane at the intersection of the bottom electrodes and the trenches. To characterize the in-plane strain, an array of 4 μm diameter aluminum dots is deposited on each actuator. The position of each dot is tracked, allowing displacement and strain profiles to be measured as a function of voltage. The uniaxial strain reaches 4.7% at 2.9 kV with a 0.2 s response time, sufficient to stimulate most cells with relevant biological strains and frequencies.

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“…So the instability will induce electrical breakdown of the dielectric elastomer, which means the breakdown field is equal to the critical field for the instability 9,12,14 . It is common that the air bubble traps in the interface when measuring the breakdown fields of dielectric elastomers 45 and no comment on avoiding air bubble has been reported. Therefore, the measured breakdown fields are probably the critical fields for the electro-creasing instability in soft dielectric films.…”

Section: Outreachmentioning

confidence: 99%

“…measured the breakdown field of VHB, one of the most widely used soft dielectric, as shown in figure 14(a) 45 . One of explanations for this enhancement is the reduction of defect density 4.45 .…”

Section: Outreachmentioning

confidence: 99%

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Mechanical constraints enhance electrical energy densities of soft dielectrics

Zhang

Wang

Zhao

2011

Applied Physics Letters

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In this thesis, a new method---mechanical constraint to increase the energy density of soft dielectrics is described. Electromechanical breakdown is one of the main factors limiting the energy density and it is induced by instabilities. Pull-in instability has been widely investigated and a theoretical model has been developed. A new type of instability-creasing to cratering instability is observed in soft dielectrics. A theoretical model is developed and shows perfect consistent with the experimental

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Actuation response of polyacrylate dielectric elastomers

Cited by 90 publications

References 8 publications

Interpenetrating Polymer Networks for High‐Performance Electroelastomer Artificial Muscles

Interpenetrating Polymer Networks for High‐Performance Electroelastomer Artificial Muscles

Microfabrication and characterization of an array of dielectric elastomer actuators generating uniaxial strain to stretch individual cells

Mechanical constraints enhance electrical energy densities of soft dielectrics

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