High-performance soft ionic biopolymer actuators based on sulfonated chitosan-coated electrospun silk membrane with graphene electrodes

Recently, there has been significant interest in the development of high-performance electroactive ionic actuators that possess biocompatible, biodegradable, and bio-friendly characteristics for use in human-attachable electronics. However, research on biopolymer-based soft actuators has been relatively limited due to challenges such as the low ionic conductivity of biopolymers, difficulty in processing to achieve desired functionalities, and improper mechanical stiffness. Therefore, in this study, an electrospun silk membrane coated with sulfonated chitosan, in which membrane exhibits stable mechanical and electrochemical properties due to its interdigitated structures, is utilized to realize high-performance ionic biopolymer actuators. In particular, the introduction of sulfonated chitosan-ionic liquid on electrospun silk lowers the mechanical stiffness and increases the ionic conductivity, resulting in the provision of ion pathways through the interdigitated silk-chitosan domain. On bare electrospun silk membrane, the ionic electrospun silk-sulfonated chitosan actuators with graphene-PEDOT:PSS electrodes show a 165% increase in bending performance compared to those with only PEDOT:PSS electrodes. The developed biopolymer actuator, which shows substantial improvement in actuation performance, can be a promising candidate for use in skin-attachable and biomedical devices.