“The paper improves our understanding of the mechanics of the support bed used for manufacturing parts by 3D bioprinting”Liam Grover
Researchers from the University of Birmingham in the UK have developed an innovative approach to the 3D printing of soft materials with additive manufacturing. The printing of biomaterials such as gels and collagens was shown to be improved by suspended layer additive manufacturing (SLAM), a technique based on a polymer-based hydrogel where the particles are manipulated to develop a self-healing gel, with potential in the production of replacement biomaterials such as heart valves and blood vessels, or even biocompatible plugs to treat bone and cartilage damage.
As reported in Advanced Functional Materials [Senior et al. Adv. Funct. Mater. (2019) DOI: 10.1002/adfm.201904845], their approach surmounted the typical problem with printing soft materials, that a lack of support means they droop and lose their shape. SLAM involves particles in the gel that can be sheared or twisted so they separate but retain some connection, an interaction that provides a self-healing effect where the gel can support the printed material during development so it doesn’t collapse under its own weight, and there is no leaking or sagging as liquids and gels can be injected directly into the medium before being built up in layers.
The study improves on existing techniques for fabricating complex 3D structures in a supportive gel bed, such as freeform reversible embedding of suspended hydrogels (FRESH), which use gels pulverized to a slurry into which the printed material is injected, but involves frictions within the gel medium that can distort printing. In FRESH, the part is supported by gel that has been broken up after processing, while in SLAM shearing is achieved during gel formation, bringing faster healing of the bed and allowing for greater complexity. Objects can be fabricated from two or more different materials, and even more complex soft tissue types, or drug delivery devices, that depend on different rates of release can be produced.
The fluid-gel material is produced by shearing a hydrogel during the gelation process so that the material forms a self-healing matrix that then heals to support the structure deposited within it. As team leader Liam Grover told Materials Today, “The paper improves our understanding of the mechanics of the support bed used for manufacturing parts by 3D bioprinting”. These supporting beds could find many applications to support the manufacture of parts, and the team hope other researchers will utilise the method to produce complex structures from soft materials. They have also initiated work based on the supporting phase to enable the creation of complex tissue structures by immobilising tissue fragments to evaluate how the bone healing process can be encouraged.
"Fabrication of complex structures by SLAM using gellan. A) Intricate lattice prior to (left) and following extraction (right) from the fluid-gel bed. B) T7 intervertebral disc as a CAD file (left) and demonstrating the printing of bulk structures with lateral (middle) and apical (right) views. C) Intricate bulk structure in the form of a gellan spider. D) Carotid artery as a CAD file (left) and during 3D printing (right). D) Tubular structure (left) demonstrating material durability (middle) and perfusibility. Scale bars = 10 mm."