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Karle has a lot of experience with human limbs, because she volunteers with a nonprofit group that 3D prints prosthetic arms for children and makes its designs available for free. She told Ars that she's fascinated by objects that go inside the body, as well as how parts of our bodies can live outside us. With her new project "Regenerative Reliquary," currently on display at the Pier 9 space in San Francisco, she has brought all her obsessions together to create an actual hand grown from human stem cells on a 3D printed trellis.

Working with bioscientist Chris Venter in Pier 9's Bio/Nano Lab and Autodesk materials scientist John Vericella, Karle designed a bone trellis in CAD based on the dimensions of her own hand. This trellis, which looks like a cross between a skeleton and a piece of jewelry, is made from pegda, a hydrogel used as a cellular growth medium in petri dishes and elsewhere. Its structure is modeled on the trabecular structure of the spongy microlattices within bone that make it flexible. For several weeks, she and her collaborators worked on 3D printing a pegda trellis on the Ember printer that would hold together inside a bioreactor where cells could grow. In the gallery above, you can see the hand inside a bioreactor, as well as what the trellis looks like under magnification. Next, she needed a cell line to grow on the trellis. Karle told Ars that she'd hoped at first to harvest her own stem cells or to use cancer cells from a mouse. But both of those options raised safety issues, so she and the scientists settled for using human mesenchymal stem cells, extracted from bone marrow (of course you can order human stem cells online). Currently, Karle is culturing the cells, and the next step in her project will be to grow them on the hand trellis. Once the project is complete, Karle will post instructions on how to build your own hand on the DiY site Instructables.

As she waits for her project to mature, so to speak, Karle's experimenting with other ways to build body parts with 3D printers at Pier 9—you can see these in the gallery above. She never got her exoskeleton, but she did 3D print a dress that looks like an exoskeleton. She's studied skeletal structures at the California Academy of Sciences in order to produce her own alien-esque vertebrae and skulls. She has also grown crystals out of a lattice, in abstract imitation of what it's like to grow flesh on a tissue trellis. Karle's work is a reminder that our bodies are built out of molecules and atoms that are inanimate but take on life when brought together in the right patterns. To repair our bodies, we must first take them apart. In Karle's work, this basic truth takes on a horrifying beauty.