Carbon nanomaterials-PEDOT: PSS based electrochemical ionic soft actuators: Recent development in design and applications

Poly(3,4-ethylenedioxythiophene): poly (styrenesulfonate), namely, PEDOT: PSS or PP as one branch of conductive polymers (CPs) which can effectively transform electrical energy to mechanical energy, has been applied in many fields including electrochemical ionic soft actuators (EISAs), in terms of its high conductivity (0.1∼ 3000 S/cm-1), small band gap (1.6–1.7 eV), low redox potential, good durability, good chemical and thermal stability, excellent mechanical properties, and adjustability. Furthermore, when PP as active binders are mixed with nanomaterials, they can not only be used to disperse nanomaterials and prevent their aggregation, but also efficiently enhance mutual conduction, specific surface aera, and redox activity. Here, an extensive review on PP-based EISAs including PP-carbon nanomaterials and PP-non carbon nanomaterials is reported, highlighting their structure and fabrication, electrochemical properties, actuation performance, mechanical properties, and applications. The great synergy between PP and advanced nanomaterials with diverse fabricating principles that provide sufficient ions storage space, ordered charges pathways, stiffness for high actuation displacement, fast responds and excellent flexibility is emphasized. Furthermore, the novel applications of EISAs toward smart devices and soft robots are also summarized. Finally, the review also proposed the current challenges and further prospect of EISAs.