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Micromachines 2017, 8(11), 339; https://doi.org/10.3390/mi8110339

Exploiting Stretchable Metallic Springs as Compliant Electrodes for Cylindrical Dielectric Elastomer Actuators (DEAs)

Department of Mechanical Engineering, National Taiwan University, Taipei 10617, Taiwan
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Received: 21 October 2017 / Revised: 17 November 2017 / Accepted: 17 November 2017 / Published: 22 November 2017
(This article belongs to the Special Issue Locomotion at Small Scales: From Biology to Artificial Systems)
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Abstract

In recent years, dielectric elastomer actuators (DEAs) have been widely used in soft robots and artificial bio-medical applications. Most DEAs are composed of a thin dielectric elastomer layer sandwiched between two compliant electrodes. DEAs vary in their design to provide bending, torsional, and stretch/contraction motions under the application of high external voltages. Most compliant electrodes are made of carbon powders or thin metallic films. In situations involving large deformations or improper fabrication, the electrodes are susceptible to breakage and increased resistivity. The worst cases result in a loss of conductivity and functional failure. In this study, we developed a method by which to exploit stretchable metallic springs as compliant electrodes for cylindrical DEAs. This design was inspired by the extensibility of mechanical springs. The main advantage of this approach is the fact that the metallic spring-like compliant electrodes remain conductive and do not increase the stiffness as the tube-like DEAs elongate in the axial direction. This can be attributed to a reduction in thickness in the radial direction. The proposed cylindrical structure is composed of highly-stretchable VHB 4905 film folded within a hollow tube and then sandwiched between copper springs (inside and outside) to allow for stretching and contraction in the axial direction under the application of high DC voltages. We fabricated a prototype and evaluated the mechanical and electromechanical properties of the device experimentally using a high-voltage source of 9.9 kV. This device demonstrated a non-linear increase in axial stretching with an increase in applied voltage, reaching a maximum extension of 0.63 mm (axial strain of 2.35%) at applied voltage of 9.9 kV. Further miniaturization and the incorporation of compressive springs are expected to allow the implementation of the proposed method in soft micro-robots and bio-mimetic applications. View Full-Text
Keywords: cylindrical dielectric elastomer actuators (DEAs); axial stretches; compliant electrodes; VHB 4905; high voltages cylindrical dielectric elastomer actuators (DEAs); axial stretches; compliant electrodes; VHB 4905; high voltages
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Liu, C.-H.; Lin, P.-W.; Chen, J.-A.; Lee, Y.-T.; Chang, Y.-M. Exploiting Stretchable Metallic Springs as Compliant Electrodes for Cylindrical Dielectric Elastomer Actuators (DEAs). Micromachines 2017, 8, 339.

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