Regulation of electrically responsive shape recovery behavior of 4D printed polymers for application in actuators

Four-dimensional (4D) printing, an additive manufacturing technology for intelligent materials and structures, has received increasing scholarly attention for its ability to achieve variable shapes, properties and functions. However, recent research has primarily focused on developing new materials and structures, neglecting the regulation of deformation behavior. We hereby propose a novel photocuring 4D printing strategy for electrically responsive shape memory polymers (E-SMPs) actuators embedded with a dual-layered electrothermal layer (ETL) and channel. One way to achieve tunable shape recovery behavior in E-SMPs is to regulate the heat generation behavior of ETL by introducing a coolant into the channel. The electric heating and water cooling were sequentially and simultaneously activated to achieve suspension of the shape recovery process and reduction in the shape recovery rate, respectively. E-SMPs embedded with single and double ETLs were utilized to evaluate their electrically-induced heating behavior, electrically responsive shape recovery behavior, and shape recovery force. Additionally, sequential shape recovery behavior was achieved by serially interconnecting three (3) ETLs with varying thicknesses. Furthermore, the channel integrated within the SMPs were employed to realize remote thermally responsive shape recovery (T-SMPs), for which the shape recovery rate was regulated by adjusting the flow rate of hot water and channel dimensions. This strategy was successfully demonstrated for manufacturing ESMPs actuators with adjustable shape recovery rate, sequential recovery behavior, and high-load deformation capability.