ABSTRACT
4D (bio-)printing endows 3D printed (bio-)materials with multiple functionalities and dynamic properties. 4D printed materials have been recently used in biomedical engineering for the design and fabrication of biomedical devices, such as stents, occluders, microneedles, smart 3D-cell engineered microenvironments, drug delivery systems, wound closures, and implantable medical devices. However, the success of 4D printing relies on the rational design of 4D printed objects, the selection of smart materials, and the availability of appropriate types of external (multi-)stimuli. Here, this work first highlights the different types of smart materials, external stimuli, and design strategies used in 4D (bio-)printing. Then, it presents a critical review of the biomedical applications of 4D printing and discusses the future directions of biomedical research in this exciting area, including in vivo tissue regeneration studies, the implementation of multiple materials with reversible shape memory behaviors, the creation of fast shape-transformation responses, the ability to operate at the microscale, untethered activation and control, and the application of (machine learning-based) modeling approaches to predict the structure-property and design-shape transformation relationships of 4D (bio)printed constructs.
ABSTRACT
In recent years, significant advancements have been made in developing architected materials, known for their benefits like being lightweight, customizable mechanical performance, and excellent energy absorption. The capabilities of 3D printing technology have facilitated the emergence of a diverse range of architected structures, featuring various unit cell types and geometries for different applications. This study explores the unique opportunity offered by multimaterial 3D printing in fine-tuning the mechanical performance of architected structures. The exploration of the programmability of these structures involves a systematic assessment of various material candidates. After careful evaluation, the selection process led to the choice of PLA and PCL biopolymers for the multimaterial structure. Experimental results emphasize the key role of design configurations in influencing mechanical characteristics, particularly in enhancing the energy absorption capacity of architected structures. By skillfully manipulating the local structure and composition through the synergistic combination of soft and hard materials, the study demonstrates the ability to achieve a diverse range of mechanical responses. The discovered insights present a promising approach that holds applicability in the design and development of multifunctional devices. This is especially significant in the biomedical field, where there is a growing demand for versatile devices.
