Printing a trachea is much like printing any object, although it requires a bit more patience. MakerBot printers use a technique called extrusion printing, which creates objects out of successive thin layers of molten plastic that bind together as the printed object cools. Printing a tracheal replacement requires alternating layers of plastic and bio-ink. That means waiting for each layer of plastic to cool so its heat doesn’t kill the living cells. Goldstein says the plastic models take about five minutes to print but the replacement trachea itself takes several hours.

Once the printer has finished the final structure, the trachea-to-be is transferred into a modified incubator, where the cells continue to grow around the plastic. The whole structure would then be inserted by a surgeon into a patient. Goldstein took an old incubator that the institute was going to decommission and is adapting it to grow his tracheae. He 3D-printed new parts—gears, screws, fittings—using models he found on MakerBot’s 3D model repository, the Thingiverse, to make the incubator, as he said, more like a rotisserie oven on the inside, so the cells are warmed evenly. “It looks like a Game Boy now,” Goldstein said.

Goldstein’s incubator, retrofitted with 3D-printed parts, would make for a very complicated Game Boy.
Goldstein’s incubator, retrofitted with 3D-printed parts, would make for a very complicated Game Boy.
Image: Quartz/Mike Murphy

Goldstein presented his work last month to the Society of Thoracic Surgeons. A representative for the US Food and Drug Administration told Quartz that the administration has not approved any 3D printers for human use, but it has “significant scientific interest in this topic.” It’s uncertain when the first trial of 3D-printed human tissue could happen, but it does seem likely to be a question of if, not when.

Other 3D models printed by Goldstein’s team.
Other 3D models printed by Goldstein’s team.
Image: Quartz/Mike Murphy

In the meantime, Goldstein’s research continues. He said MakerBot has provided him with a new type of filament made primarily of PLA plastic and limestone, which is not yet available to the general public. Limestone is made almost entirely of calcium carbonate, which is also found in bones. While Goldstein couldn’t say how he was using this filament in research, he spoke of a future where doctors could theoretically replace parts of damaged bones with 3D printed materials.

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