Decroly Gilles, Raffoul Romain, Deslypere Clara, Leroy Paul, Van Hove Louis, Delchambre Alain, Lambert Pierre
TIPs Dpt, Université Libre de Bruxelles, Brussels, Belgium.
BEAMS Dpt, Université Libre de Bruxelles, Brussels, Belgium.
Front Robot AI. 2021 May 10;8:672934. doi: 10.3389/frobt.2021.672934. eCollection 2021.
Phase-change material-elastomer composite (PCMEC) actuators are composed of a soft elastomer matrix embedding a phase-change fluid, typically ethanol, in microbubbles. When increasing the temperature, the phase change in each bubble induces a macroscopic expansion of the matrix. This class of actuators is promising for soft robotic applications because of their high energy density and actuation strain, and their low cost and easy manufacturing. However, several limitations must be addressed, such as the high actuation temperature and slow actuation speed. Moreover, the lack of a consistent design approach limits the possibility to build PCMEC-based soft robots able to achieve complex tasks. In this work, a new approach to manufacture PCMEC actuators with different fluid-elastomer combinations without altering the quality of the samples is proposed. The influence of the phase-change fluid and the elastomer on free elongation and bending is investigated. We demonstrate that choosing an appropriate fluid increases the actuation strain and speed, and decreases the actuation temperature compared with ethanol, allowing PCMECs to be used in close contact with the human body. Similarly, by using different elastomer materials, the actuator stiffness can be modified, and the experimental results showed that the curvature is roughly proportional to the inverse of Young's modulus of the pure matrix. To demonstrate the potential of the optimized PCMECs, a kirigami-inspired voxel-based design approach is proposed. PCMEC cubes are molded and reinforced externally by paper. Cuts in the paper induce anisotropy into the structure. Elementary voxels deforming according to the basic kinematics (bending, torsion, elongation, compression and shear) are presented. The combination of these voxels into modular and reconfigurable structures could open new possibilities towards the design of flexible robots able to perform complex tasks.
相变材料 - 弹性体复合材料（PCMEC）致动器由嵌入微气泡中相变流体（通常为乙醇）的软弹性体基质组成。当温度升高时，每个气泡中的相变会引起基质的宏观膨胀。由于其高能量密度、致动应变、低成本和易于制造，这类致动器在软机器人应用中很有前景。然而，必须解决几个限制因素，例如高致动温度和缓慢的致动速度。此外，缺乏一致的设计方法限制了构建能够完成复杂任务的基于PCMEC的软机器人的可能性。在这项工作中，提出了一种制造具有不同流体 - 弹性体组合的PCMEC致动器而不改变样品质量的新方法。研究了相变流体和弹性体对自由伸长和弯曲的影响。我们证明，与乙醇相比，选择合适的流体可增加致动应变和速度，并降低致动温度，使PCMEC能够与人体密切接触使用。同样，通过使用不同的弹性体材料，可以改变致动器的刚度，实验结果表明曲率大致与纯基质的杨氏模量的倒数成正比。为了展示优化后的PCMEC的潜力，提出了一种受折纸启发的基于体素的设计方法。PCMEC立方体通过纸模制并在外部进行加固。纸上的切口使结构产生各向异性。展示了根据基本运动学（弯曲、扭转、伸长、压缩和剪切）变形的基本体素。将这些体素组合成模块化和可重构结构可能为设计能够执行复杂任务的柔性机器人开辟新的可能性。
