The researchers call their technique the Freeform Reversible Embedding of Suspended Hydrogels, or FRESH. They begin with a scan of a real heart and translate the data into something a 3D printer can read. Because the device works by depositing layers of material one on top of another, they run the 3D image through a slicer program. “For every layer, it basically defines the path that the material is going to be extruded, and then feeds that to the printer,” says Adam Feinberg, a biomedical engineer at Carnegie Mellon University who coauthored the new paper.
Just last month, former Florida State basketball player Michael Ojo died of apparent heart complications while playing in a pro league in Serbia, shortly after the 27-year-old had recovered from Covid-19.To prevent the pandemic from leading to similarly tragic heart injuries among student athletes, doctors at Ohio State University developed a new protocol, says Saurabh Rajpal, a cardiologist and assistant professor of internal medicine at OSU.
It’s 2020. Why Do Printers Still Suck?
That printer churns out alginate—a squishy material derived from seaweed—that the researchers chose both for its low cost and likeness to the material properties of human heart tissue. But instead of it extruding it into air, as a normal 3D printer might do when building something out of plastic, this extrudes the ersatz heart into a container of support gel, specifically gelatin.“The analogy I have is: Imagine you were printing inside of hair gel,” says Feinberg. Think of the little bubbles suspended in that bottle of gel—the material is providing enough support for them to float indefinitely, or at least until you squeeze the gel out of the bottle. In this case, the gelatin offers enough give for the needle of the 3D printer to slide through. “Whatever you extrude stays embedded in place, kind of like those air bubbles in hair gel,” Feinberg says.
And now for something completely different when it comes to the art of artificial hearts: jello shots. After the organ is done printing, the researchers need a way to dissolve the gel lattice that’s surrounding it, and they use a familiar method. “I think a lot of people have experienced this from using gelatin in baking or making jello shots,” says Feinberg. “It's actually a liquid when you warm it up, but it becomes a solid gel when you cool it down. And so we take advantage of that.” When they’re ready to extract the heart, all Feinberg has to do is raise the bath to body temperature, melting away the support gel and leaving behind the 3D-printed structure.