Researchers from the University of Birmingham in the UK are developing a new 3D printing method for soft materials. The process, called Suspended Layer Additive Manufacturing (SLAM), can be used for biomaterials such as gels and collagens and could have applications in producing artificial implants for the medical sector.
3D printing soft materials comes with a range of challenges, mostly caused by gravity. That is, as they are printed into a structure, soft materials tend to succumb to gravity, sagging or completely losing their shape. A search for solutions has led to some unlikely places, like 3D printing in space for zero gravity environments. More commonly, however, researchers have explored the potential of printing soft materials inside a vat of a denser material, to offer support during the printing.
This is the case with the SLAM process, which uses a polymer-based hydrogel as a base in which biomaterial particles can be injected and built into various structures and shapes. The hydrogel material pioneered by the University of Birmingham team is special in that it integrates particles that create a self-healing gel.
Compared to other similar approaches—including Freeform Reversible Embedding of Suspended Hydrogels (FRESH)—which use gels that have been minced to form a slurry bath, the SLAM hydrogel has less of a risk of distortion caused by friction.
“The hydrogel we have designed has some really intriguing properties that allow us to print soft materials in really fine detail,” explains Professor Liam Grover, who led the research project. “It has huge potential for making replacement biomaterials such as heart valves or blood vessels, or for producing biocompatible plugs, that can be used to treat bone and cartilage damage.”
In a recent study published in the journal Advanced Functional Materials, the research team from the School of Chemical Engineering, demonstrated how the SLAM 3D printing process enabled them to shear or twist particles in the hydrogel base, causing them to separate while still retaining a connection. This interaction, the researchers say, results in a self-healing effect which allows the gel to support the printed soft material without sagging or leaking.
The study reads: “Upon extrusion of a bioink into the fluid‐gel matrix, the deposited bioink is suspended in its liquid state, and collapse of the printed structure is prevented prior to gelation. This approach enables very good layer integration as no gelation is initiated during the printing process. This also allows the production of constructs from two or more different materials that have dissimilar physicochemical and mechanical properties thus creating a printed part with distinct anisotropic physical behavior.”
The SLAM technique can reportedly also accommodate two or more materials within the same print, opening up numerous possibilities for printing complex soft tissues or drug delivery devices with varying release rates.