Designing Functional 4-Dimensional Biomaterials for Soft Tissue Applications
There is substantial interest in designing polymer systems to include temporally-related functionalities (4D materials), such as degradation, swelling, and shape memory. Shape memory polymers (SMPs), one class of 4D material, have been of great interest in the biomaterials community since their development as they may offer avenues towards minimally invasive medical technologies. However, these advancements have been difficult to realize across the majority of clinical treatments, and the additive manufacturing (AM, 4D printing) of such materials has been limited.
Polyurethane-based SMP foams, a more conventionally processed 4D material, were introduced as a promising technology for producing low density materials which support tissue healing in void filling applications. The role of these materials in clinical applications is briefly discussed for cardiovascular materials, primarily as a springboard for subsequent studies focusing on the need for rational polymer/monomer design through the comparison of SMP foams with AM-produced 4D printed scaffolds. The role of monomer design and material properties is discussed, centering around achieving materials for 3D printable soft tissue biomaterials. Comparisons are drawn between these processing and synthetic techniques (foaming vs AM), to showcase the power of controlled polymerizations and 4D printing in biomaterials. Application-specific examples focus on the biocompatibility, as determined through in vitro and in vivo studies, and the extension towards clinically relevant polymer synthesis. The expansion of this work, including additional functionalities that may be achieved, are also discussed to provide insight for future research and direction.
Andrew Weems is currently a Marie Curie Research Fellow at the University of Birmingham in the United Kingdom. He received his PhD from Texas A&M University, in biomedical engineering, focusing on the development of shape memory polyurethane foams for cardiovascular medical devices, such as aneurysm occlusive therapies. His post-doctoral work has been at the University of Warwick and the University of Birmingham, both with Professor Andrew Dove, developing novel materials and techniques in photopolymerizations. Overall, his work, which has been publicized by Bruker, the Royal Society of Chemistry, and NASA, has focused on designing polymeric biomaterials, ranging from monomer synthesis to bulk material modifications and processing. These studies have been utilized in the regulatory submission of two medical devices currently in humans (with the startup company Shape Memory Medical Inc), as well as resulting in the formation of a UK-based spinout company 4D Medicine Ltd. He has received funding from the RSC, Innovate UK, the EU’s Marie Sklodowska-Curie International Fellowship, NASA’s Jenkins Fellowship, the Whitaker Foundation, the UK’s EPSRC, and university-specific funding in both the US and the UK.