Effect of Structure Parameters of 4D-Printed Actuators on Time-Depend Behavior: Experiment, Modeling and Design

Abstract Four-dimensional (4D) printing, an innovative advancement emerging from additive manufacturing, introduces a transformative approach to creating dynamic artifacts. This cutting-edge technology employs shape memory polymers as its core material, enabling the production of items that evolve and adapt over time in a pre-programmed manner. Central to this process is fused deposition modeling, a technique pivotal in realizing the self-assembly of functional structures that exhibit time-dependent behaviors. The essence of 4D printing lies in its ability to program artifacts for specific time-dependent deformations, a feature that demands meticulous control to avert any potential motion interference. This study delves into the intricate dynamics of a 4D-printed bilayer actuator, scrutinizing the interplay of various parameters that govern its time-dependent behavior. This study investigates the effects of parameters in terms of design parameter (the ratio of thickness) and printing parameters (printing speed, printing temperature and printing height) of a 4D-printed bilayer actuator. The results show that (i) The ratio of thickness emerges as a simple yet effective design principle crucial for controlling the speed of the actuator’s time-dependent self-folding mechanism. This insight opens up avenues for precision in designing 4D printed objects. (ii) The increase in printing speed leads to a corresponding increase in the speed of time-dependent deformation. In contrast, augmenting the printing temperature, layer height, or the overall height of the actuator yields a slowing effect on this time-dependent deformation process. (iii) The ratio of the two layers within the bilayer actuator influences the speed of time-dependent deformation in an opposing manner compared to other parameters. Building upon these findings, the study introduces a response surface model that intricately relates all the printing parameters to the time-dependent deformation behavior of the actuators. The model provides a comprehensive framework for understanding and manipulating the time-dependent deformation behavior of structures in 4D printing. By judiciously designing the bilayer actuators and optimizing the printing parameters, it becomes feasible to fabricate 3D printed structures that respond swiftly to thermal stimuli and exhibit a controlled, sequential, time-dependent shape-changing ability. These programmed time-dependent actuators play a crucial role in shaping the future of 4D printing technology, enabling the creation of structures that can automatically fold into predefined shapes in a time-controlled manner. These time-dependent functional capabilities mark an advancement in additive manufacturing, where adaptive dynamic materials can provide unprecedented lightweight, highly flexible solutions that offer new directions for innovative applications in fields as diverse as biomedical devices and aerospace engineering.