Liu Chien-Hao, Lin Po-Wen, Chen Jui-An, Lee Yi-Tsung, Chang Yuan-Ming
Department of Mechanical Engineering, National Taiwan University, Taipei 10617, Taiwan.
Micromachines (Basel). 2017 Nov 22;8(11):339. doi: 10.3390/mi8110339.
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.
近年来，介电弹性体致动器（DEA）已广泛应用于软体机器人和人工生物医学应用中。大多数DEA由夹在两个柔性电极之间的薄介电弹性体层组成。DEA的设计各不相同，以便在高外部电压作用下提供弯曲、扭转和拉伸/收缩运动。大多数柔性电极由碳粉或金属薄膜制成。在涉及大变形或制造不当的情况下，电极容易断裂且电阻率增加。最糟糕的情况会导致导电性丧失和功能失效。在本研究中，我们开发了一种利用可拉伸金属弹簧作为圆柱形DEA的柔性电极的方法。这种设计的灵感来自机械弹簧的可扩展性。这种方法的主要优点是，当管状DEA沿轴向伸长时，类似金属弹簧的柔性电极仍保持导电且不会增加刚度。这可归因于径向厚度的减小。所提出的圆柱形结构由高度可拉伸的VHB 4905薄膜折叠在空心管内，然后夹在铜弹簧（内部和外部）之间，以便在施加高直流电压时沿轴向进行拉伸和收缩。我们制作了一个原型，并使用9.9 kV的高压源通过实验评估了该装置的机械和机电性能。该装置在施加电压增加时轴向拉伸呈非线性增加，在9.9 kV的施加电压下达到最大伸长0.63 mm（轴向应变2.35%）。进一步的小型化以及压缩弹簧的加入有望使所提出的方法应用于软体微型机器人和仿生应用中。
