Hydrogels are one of the hottest materials in biomedical research these days, as anyone following this publication will attest to. They’re biocompatible, have the squishy consistency of soft tissues, and they can be tinkered with to host living cells, deliver drugs, and hopefully one day serve as replacements for diseased tissues and organs.
Hydrogels’ unique lightness and softness, though, makes it hard to 3D print structures and living cells within them. They tend to sag, and providing internal support is very difficult without compromising some of the inherent properties of the hydrogel.
Now, researchers at Birmingham University in the U.K. have come up with a 3D printing technique that can be used to print structures within hydrogels that would otherwise easily deform. This could allow for a more accurate and predictable way of creating living tissues that can actually maintain their consistency and internal structure.
Typically, when printing within a hydrogel, the hydrogel is mixed up into a slurry. The printed material is injected into the slurry, but the injection process makes the inks diffuse out of the gel and where the inks are placed, there’s no real support to make them stay.
The Birmingham team came up with a unique formulation for a polymer hydrogel that can self-heal precisely where injections of a 3D printed material are made, creating a strong structure in the process. The magic is performed thanks to a novel application of shear forces during the gelation process.
Particles within the gel the team is working with can almost completely detach from the rest of the gel, but still maintain a modest hold, becoming stronger after the stress of the injection is relieved. Other gels are more brittle and easily let go or tear, such as gelatin. The new gel, which has a unique molecular consistency, provides a self-healing capability.
“The hydrogel we have designed has some really intriguing properties that allow us to print soft materials in really fine detail,” explains Professor Grover of Birmingham University, one of the research leads. “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.”
Study in journal Advanced Functional Materials: Fabrication of Complex Hydrogel Structures Using Suspended Layer Additive Manufacturing (SLAM)