Inspired from the nature, soft actuators have been attracting the incremental attention on account of the benefits in terms of high flexibility and safety for human operators, but material selection and manufacturing process remain challenging. Compared with the conventional actuators in solid state, smart phase change materials (PCMs) are superior for the soft actuation applications because of the capability to change their shapes or properties in response to a wide range of stimulants, such as heat, light, pH, or electrical field. This review provides a comprehensive analysis of smart PCM applications on soft actuators, including metal alloys and their polymer counterparts, shape memory materials and liquid crystalline polymers. Such materials generally exhibit large deformation degrees, high complexity in movement and diverse versatility, which are compliant and well suited for soft actuators in the vast applications of soft mechatronics and robots. Since stiffness variable plays a significant role on actuator transformation, this review focuses on smart materials with an emphasis on the different forms of phase transformation among solid, liquid, and gas phase. This review enables a better understanding of phase transformation, performances, and limitations of smart PCMs, and provides insights into the potential applications for soft actuators.

中文翻译：

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软致动器智能相变材料开发的最新进展

受自然启发，软执行器因其在高灵活性和对人类操作者安全性方面的好处而引起了越来越多的关注，但材料选择和制造过程仍然具有挑战性。与传统的固态致动器相比，智能相变材料 (PCM) 在软致动应用中具有优势，因为它能够响应各种刺激物（如热、光、pH、或电场。本综述全面分析了智能 PCM 在软致动器上的应用，包括金属合金及其聚合物对应物、形状记忆材料和液晶聚合物。此类材料一般具有变形度大、运动复杂度高、通用性强等特点，它是合规的，非常适合在软机电一体化和机器人的广泛应用中的软执行器。由于刚度变量在执行器转换中起着重要作用，因此本综述重点关注智能材料，重点关注固相、液相和气相之间不同形式的相变。本综述有助于更好地了解智能 PCM 的相变、性能和局限性，并深入了解软执行器的潜在应用。