A review of electro-active shape memory polymer composites: Materials engineering strategies for shape memory enhancement

Electro-active shape memory polymer composites represent a subset of smart materials with the ability to return to a predetermined shape when subjected to an electrical voltage, primarily due to Joule's heating. In contrast to thermo-active shape memory composites, these electro-active materials are designed to respond to indirect heating through a relatively low actuating voltage, rather than direct heating of the material. Electro-active shape memory polymer composites have garnered increasing interest with time because of the extensive control over their properties, making them prime candidates for a wide range of applications, including robotics, soft actuators, biomedical devices, and flexible electronics. This review paper delves into the state-of-the-art in the synthesis of this type of materials and provides a summary of the most significant findings of the last five years. The aim of this review paper is to provide a comprehensive insight in this topic, and to facilitate comparison of various characteristics in recently developed electro-active shape memory composites. The composition and structure of these materials are highlighted, and the shape recovery mechanisms as well as programming methods are explained. Furthermore, this review explores methods to improve the electro-active shape memory effect of these composites through the incorporation of fillers. These approaches serve to increase the conductivity, enhance filler dispersion, and lower the transition temperature, thereby extending the application potential of these materials. The paper concludes with some future perspectives on electro-active shape memory polymer composites and identifies current challenges and knowledge gaps that need to be addressed.