Exploration of the potential of polymer 4D printing: Experiments on the printing quality and the impact of temperature and geometry on the shape-changing effect

Abstract 4D printing is a term for the additive manufacturing (AM) processes, in which shape-memory materials are used. A 4D printed component is capable of changing its shape to another, which implies that the transformation over time is regarded as the fourth dimension in addition to x, y, and z dimensions in AM. A common material type for 4D printing is the shape memory polymer (SMP) which has the advantages such as low cost and high shape recovery. Under this background, this research focuses on thermoplastic polyurethane (TPU)-based SMP and systematically investigates its performance using three experiments. In the first experiment, the printing quality of the SMP with different process parameters is analyzed and evaluated by its relative material density. In the second and third experiments, the impacts of, respectively, the ambient temperature and the geometry of SMP parts on the shape-changing process are analyzed and evaluated by different time-related parameters during the process. To implement the findings from the experiments, three use cases are described.