4D Printing Shape-Morphing Hybrid Biomaterials for Advanced Bioengineering Applications

Abstract

Four-dimensional (4D) printing is an innovative additive manufacturing technology used to fabricate structures that can evolve over time when exposed to a predefined environmental stimulus. 4D printed objects are no longer static objects but programmable active structures that accomplish their functions thanks to a change over time in their physical/chemical properties that usually displays macroscopically as a shapeshifting in response to an external stimulus. 4D printing is characterized by several entangled features (e.g., involved material(s), structure geometry, and applied stimulus entities) that need to be carefully coupled to obtain a favorable fabrication and a functioning structure. Overall, the integration of micro-/nanofabrication methods of biomaterials with nanomaterials represents a promising approach for the development of advanced materials. The ability to construct complex and multifunctional triggerable structures capable of being activated allows for the control of biomedical device activity, reducing the need for invasive interventions. Such advancements provide new tools to biomedical engineers and clinicians to design dynamically actuated implantable devices. In this context, the aim of this review is to demonstrate the potential of 4D printing as an enabling manufacturing technology to code the environmentally triggered physical evolution of structures and devices of biomedical interest.

3D and 4D printing of biomedical materials: current trends, challenges, and future outlook

“…Despite modern advances, the limited availability of suitable 3D printable material and the need for a universal processing technique hinder the application of 3D printing in the medical sector. The applicability of some 3D bioprinted materials, such as medical implants, is often challenged due to low mechanical strength, biocompatibility, wear resistance, and sustainability [193]. A static 3D printed material becomes incompatible with more dynamic biological systems [194].…”

“…The main objective of 5D printing is to manufacture products with enhanced mechanical properties using less material. 5D printing has excellent potential in producing curved, complex structures of medical devices, including artificial bones and complex implants with curved surfaces and improved mechanical properties [193,195].…”

“…Moreover, the production process in 6D printing is identical to 5D printing. Interestingly, 6D printed objects are more complex and flexible, with superior mechanical properties and sensitivity [193,196]. Future research should be based on the development of novel materials for 4D and 6D printing, where a desirable change is achieved as a response to the stimulus.…”

“…Smart-printed materials with tailored structures and improved mechanical properties can be achieved when progressing from 3D to 6D printing. However, the cost of the printing device also increases with higher-order printing setups [193]. Therefore, the user needs to make educated decisions related to the selection of printing technique for each scenario.…”

“…Therefore, combining modern imaging and simulation techniques is imperative for conducting successful clinical procedures using AM materials. In future AM, emphasis should also be given to contactless manipulation stimuli that can cause changes in the materials without physical contact [193].…”