Four-Dimensional Printing of Multi-Material Origami and Kirigami-Inspired Hydrogel Self-Folding Structures

• Published in: Materials Vol. 17; no. 20; p. 5028
• Main Authors: Appavoo, Divambal, Azim, Nilab, Elshatoury, Maged, Antony, Dennis-Xavier, Rajaraman, Swaminathan, Zhai, Lei
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 15-10-2024; MDPI
• Subjects: 3-D printers; 3D printing; Bend properties; Control equipment industry; Design; Flexibility; Folding; Folding structures; Hydrogels; Material properties; Mechanical properties; Polyethylene glycol; Polymers; Polyols; Predictive control; Robotics; Simulation methods; Structural design; Tensile strength; Three dimensional printing; United States; United States > US; double layer; 4D printing; poly(N-iso-propylacrylamide); stimuli responsive; hydrogel
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma17205028

Four-dimensional printing refers to a process through which a 3D printed object transforms from one structure into another through the influence of an external energy input. Self-folding structures have been extensively studied to advance 3D printing technology into 4D using stimuli-responsive polymers. Designing and applying self-folding structures requires an understanding of the material properties so that the structural designs can be tailored to the targeted applications. Poly(N-iso-propylacrylamide) (PNIPAM) was used as the thermo-responsive material in this study to 3D print hydrogel samples that can bend or fold with temperature changes. A double-layer printed structure, with PNIPAM as the self-folding layer and polyethylene glycol (PEG) as the supporting layer, provided the mechanical robustness and overall flexibility to accommodate geometric changes. The mechanical properties of the multi-material 3D printing were tested to confirm the contribution of the PEG support to the double-layer system. The desired folding of the structures, as a response to temperature changes, was obtained by adding kirigami-inspired cuts to the design. An excellent shape-shifting capability was obtained by tuning the design. The experimental observations were supported by COMSOL Multiphysics
software simulations, predicting the control over the folding of the double-layer systems.