However, a team of researchers from the University of Florida have developed a process that allows previously impossible structures to be 3D printed out of soft materials like human cells or even flexible electronic circuits. The process works by injecting inks loaded with the 3D printing material into a special gel that will hold them in place and prevent them from collapsing in on themselves. This technique could eventually be harnessed to build complex, 3D printed organs from some of a patient’s own cells. And while printing new, viable organs is still a ways off, the process could be useful sooner as a way to create incredibly lifelike surrogate organs for medical training or drug research.
What makes this new 3D printing process possible is a commercially available granular hydrogel called Carbopol EDT 2020. The Carbopol gel is made of particles that are only 7 micrometers wide, which allows it to act as both a liquid and a solid depending on the shear stress that is applied to it. The unique properties of the gel also allow the extruder from the tiny printer to penetrate the gel and deposit the printing medium without disrupting the rest of the structure being printed. The gel holds the printing inks firmly in place so virtually any complex object can be drawn into it. The research team has used the gel to 3D print complex shapes like a tube tied in a knot, a set of tiny Russian nesting dolls and even detailed models of jellyfish.
“The granular gel medium yields, fluidises, flows and self-heals locally and rapidly around the moving printing needle. When the inks are printed into the gel, they are trapped. 3D printing is no longer a game of specially made solidifying materials or optimally matched support materials,” explained University of Florida researcher Thomas Angelini to Chemistry World.
While this is not the first 3D bioprinting process that has experimented with using a suspended liquid to act as printing support, it is the use of this specific gel medium that makes it novel. However there are still hurdles to be overcome; so far the printing process is still rather slow, so larger structures will take far too long to print, possibly too long for any living tissue to remain viable. Additionally, it can often be difficult to remove the bioprinted matter from the gel. But Angelini and his team are currently working to develop new granular hydrogels that allow for bioprinted matter to be separated from it quicker while reducing the risk of damaging the construct.
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