Development of an electro-thermo-mechanical 4D printed multi-shape smart actuator: experiments and simulation

This investigation presents an experimental and numerical approach to developing 4D printed multi-shape actuators with an integrated electrical self-triggering system. It employs a multifunctional shape memory carbon black Polylactic Acid (PLA) layer embedded within rubbery thermoplastic polyurethane (TPU). Notably, these thermo-responsive actuators are programmed and triggered using Joule’s effect, eliminating the need for an external heat source and enabling precise control of temperature gradients. Two distinct motion mechanisms are employed: the differences in thermal expansion coefficient between the PLA/TPU polymers below the glass transition temperature, and the shape memory effect of the PLA layer above the glass transition temperature. As a result, a diverse range of motion responses can be achieved by adjusting the potential differences. A coupled electro-thermo-mechanical finite element model is used to gain further insight into the motion mechanisms, offering predictive capabilities beyond the ones reported by previous models. The developed technology provides enhanced actuation capabilities to conventional bi-shape SMP actuators, offering a versatile range of bending cycles. Furthermore, Joule’s effect enables the implementation of closed-loop control systems, which is essential for developing autonomous robotic systems.