Latest Advances in Development of Smart Phase Change Material for Soft Actuators

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.