4D printing is the process of adding smart material layer by layer to create objects that can change shape or behavior over time [1] [2]. Among various additive manufacturing (AM) processes, fused filament fabrication (FFF) is an economical and robust method of processing thermo-responsive shape memory polymer. For creating nature-inspired structures using 4D printing, it is necessary to control the shape-morphing behavior [3]. The present work reports the effect of various printing process parameters and their optimization for different programming strategies applied to FFF 4D printing of PLA-SMP. Variations in morphing behavior are characterized by ratios of shape recovery (Rr), shape fixation (Rf) by using an economically viable in-house developed testing setup along with a uniquely designed methodology, applied for various programming methods and printing parameters to be useful for a controlled shape-changing behavior. Utilizing a response surface methodology (RSM) based design of experiment (DoE) to get an analysis of variance (ANOVA), it is found that the most important process parameters affecting the shape morphing behavior are nozzle temperature and printing speed. A regression-based prediction model is developed, and parametric optimization is done to get high Rr and Rf. On further comparison between the two programming methodologies, it is found that the one programmed during the printing process shows better results than the other. Finally, a bending actuator with controlled actuation has been accomplished, and nature-inspired 4D-printed honeycomb prototypes have been made to demonstrate its thermo-responsive actuation.

References

[1] B. B. Samal, A. Jena, and D. Mishra, “Controlled Shape Changing Components by Using 4D Printing Technology,” in 10th International Conference on Precision, Meso, Micro and Nano Engineering (COPEN 10), IIT Madras, 2017, no. October, pp. 78–81. Accessed: Feb. 05, 2021. [Online]. Available: http://www.copen.ac.in/proceedings/copen10/copen/19.revised_manuscript_262.pdf

[2] B. B. Samal, A. Jena, and D. Mishra, “Indian Researchers Develop World’s Strongest 4D Printed Parts,” Manufactur3D magazine, 2018. Accessed: Jan. 28, 2020. [Online]. Available: https://manufactur3dmag.com/indian-researchers-develop-worlds-strongest-4d-printed-parts/

[3] B. B. Samal, A. Jena, S. K. Varshney, and C. S. Kumar, “4D printing: An experimental case study on processing of shape memory polymer by FDM/FFF for nature inspired structures,” in Advances in Additive Manufacturing Artificial Intelligence, Nature-Inspired, and Biomanufacturing, A. Kumar, R. K. Mittal, and A. Haleem, Eds. Elsevier, 2023, pp. 361–377. doi: https://doi.org/10.1016/B978-0-323-91834-3.00019-3.