Experimental Investigations into 4D Printing of Biocompatible Triple-Shape Memory Polymer Structures

In this work, a triple-shape memory polymer was developed by solution blending of poly(lactic acid) (PLA) with poly(propylene carbonate) (PPC), which was 3D printed using the material extrusion principle. The blend of crystalline PLA and amorphous PPC enabled it to attain tunable mechanical properties. Morphological observations of blended PLA/PPC samples revealed a phase-segregated morphology, resulting in the appearance of two distinct glass transition temperatures, exhibiting a triple-shape memory effect (triple-SME). The PLA50/PPC50 composition achieved an optimum shape-fixity ratio (95.63%) and shape-recovery ratio (96.26%) due to the existence of a cocontinuous phase morphology. As a proof of concept, 4D printing of the PLA50/PPC50 composition was demonstrated at body temperature as a potential biomedical application to facilitate minimally invasive surgery. The in vitro degradation study of the PLA50/PPC50 composition resulted in a 7.5% mass loss over a period of 56 days. Finally, the in vitro cytotoxicity of all 3D printed PLA/PPC blends demonstrated excellent biocompatibility, proving their potential as an implant for tissue engineering applications. The elucidation of the parameters influencing the selective actuation of triple-SME gained from this study is expected to open a wide range of possibilities for use in biomedical devices.