Imagine having the option to get a 3D-printed organ. Well, a team of biomedical engineers from Carnegie Mellon University has just developed the first flexible, full-size, 3D-print of a human heart, bringing us one step closer to that reality.

Additive manufacturing printers are popular, but are typically known to build hard objects using materials like plastic or metal. But rigid plastic organs aren’t very practical. These printers could be used with softer materials, like biological hydrogels — you know, to make a heart — but those tend to collapse mid-print. But this new method can change the game.

The 3D-printing technique is called Freeform Reversible Embedding of Suspended Hydrogels or FRESH. It can print biological structures with soft squishy materials like alginate, a biomaterial made from seaweed, which feels like human tissue. AND it cleverly solves that collapsing problem during print by suspending flexible materials inside a container of gelatin.

For this team of researchers it all starts with a MRI scan from a real heart. The scan gets “chopped-up” digitally into horizontal slices by a program which then translates them into code that a printer will understand. A needle-like nozzle moves through the gelatin support bath, extruding thin layers of alginate. The layers stack on top of each other to build the shape. When the print is complete, it’s put in an incubator overnight, where the temperature is raised to 37°C to gently melt away the gelatin support structure, leaving only the 3D-printed heart.

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