In the intro to the HBO sci-fi series Westworld, a 3D printer produces humanoid robots, delicately assembling the incredible intricacies of the human form so these robots can continue to – spoiler alert – do naughty things. After all, it takes a lot of biomechanical coordination to murder large numbers of people in the flesh.
Speaking of: Researchers have just made a scientific leap to make 3D printed flesh and blood a reality. Writing recently in the newspaper ACS Biomaterials Science & Engineering, one team described how they reused a low-cost 3D printer into a printer capable of turning an MRI of a human heart into a full-size deformable analogue that you can actually hold in your hand. Tighten it, and it’ll look like the real thing. Open it and you will find rooms. The idea is not to one day carry out the homicidal humanoids of Westworld, but to give surgeons a better way to practice on a patient’s heart before an operation. This breakthrough could eventually lead to fully functional 3D printed hearts and give medical device developers an unprecedented platform to test their products.
The researchers call their technique the reversible incorporation of free form suspended hydrogels, or FRESH. They start with a scan of a real heart and translate the data into something a 3D printer can read. Since the device works by depositing layers of material on top of each other, they run the 3D image through a cutting program. “For each layer, it basically sets the path in which the material is going to be extruded and then passes it to the printer,” says Adam Feinberg, a biomedical engineer at Carnegie Mellon University who co-wrote the new paper.
This printer produces alginate – a spongy material derived from marine algae – which the researchers chose both for its low cost and its resemblance to the material properties of human heart tissue. But instead of extruding through air like a normal 3D printer might do when building something out of plastic, this extrudes the ersatz core into a container of supporting gel, especially gelatin. .
“The analogy I have is this: Imagine printing inside a hair gel,” says Feinberg. Think about the tiny bubbles suspended in that gel bottle – the material provides enough support for them to float around indefinitely, or at least until you squeeze the gel out of the bottle. In this case, the gelatin offers enough gelatin for the needle of the 3D printer to slide. “Everything you extrude stays in place, much like those air bubbles in the hair gel,” says Feinberg.
And now for something completely different when it comes to the art of artificial hearts: jello shots. Once the organ has finished printing, the researchers need a way to dissolve the gel network around it and use a familiar method. “I think a lot of people have experienced this by using gelatin in baking or making jello shots,” Feinberg says. “It’s actually a liquid when you heat it up, but it becomes a solid gel when you cool it. And so we take advantage of it. When they’re ready to extract the heart, all Feinberg has to do is raise the bath to body temperature, melt the support gel, and leave the structure 3D printed.