Magnetorheological elastomer-based 4D printed electroactive composite actuators

Magnetorheological elastomer (MRE) composite actuators are extraordinary since they can be controlled remotely, move swiftly, adapt to rough surfaces, and engage with humans in a secure manner. Despite all these advantages, pure MREs are not stable enough because of their high degree of softness. Also, a magnetic field is always required to actuate and hold them in the required position accordingly. This paper offers a new conceptual design for bi-stable MRE-based electroactive composite actuators with high performance. The idea is a combination of MRE composites and 4D printing (4DP) of conductive shape memory polymers. The silicone resins are loaded with strontium ferrite magnetic particles and a thin conductive carbon black polylactic acid (CPLA) is 4D printed and embedded as a core inside the composite. A set of parametric studies is carried out to examine the material properties, 4DP characteristics, and magnetization conditions. As an outcome, a functional, lightweight, and bi-stable composite actuator with programmable magnetic patterns is developed. This actuator can be positioned in the actuated situation without any stimuli as long as required. The shape memory behaviour, bi-directionality, and remote controlling of the composite actuator are driven by Joule heating and magnetic fields. The actuator with a weight of 1.47 g can hold and lift weights up to 200 g. Finally, experiments are conducted to demonstrate the immense potential of the developed composite actuators as mechanical and biomedical devices. Due to the absence of similar concepts and results in the specialized literature, this paper is likely to advance the state-of-the-art smart composite actuators with remotely controlled shape-memory features.