Energy Consumption Modeling of 4D Printing Thermal-responsive Polymers with Integrated Compositional Design for Material

The emergence of 4D printing has revolutionized the additive manufacturing industry by enabling dynamic shape memory effects ensured by the use of smart materials. In addition to 3D fabrication, 4D printed products need to undergo shape programming and recovery cycles to achieve desired shape memory effects. Due to the new process and material characteristics, energy consumption models established for 3D printing are no longer applicable for 4D printing. In current literature, the environmental sustainability for 4D printing has not yet been evaluated, leading to unknown environmental impacts that could be caused by 4D printing processes and/or materials. In this research, theoretical models for quantifying the energy consumption in 4D printing thermal-responsive polymers are established by jointly considering the compositional design for materials. Experiments and case studies are performed to validate the proposed models and further investigate some critical factors that can affect energy consumption, e.g., values of process parameters like layer thickness, and thermo-temporal conditions in shape memory cycles. The case study results show that overall energy consumption can be reduced by 1) increasing the concentrations of multi-functional crosslinkers in material composition, and 2) setting the shape programming and recovery temperatures as 10 to 15 degrees C above the material glass transition temperature without compromising the shape fixity and recovery ratios. In addition, by adjusting the influential parameters throughout different stages in 4D printing, the total energy consumption can be reduced by 37.33%, which corresponds to a reduction of 259.52 pounds of CO2 emissions per kilogram methacrylate resin.