Doesn’t look much like an organ – yet (Image: David Gamradt/University of Iowa)

You might be able to knit a pair of socks, but robots could one day knit you a pair of kidneys. Bioprinters with many arms could coordinate their limbs to knit together different types of human tissue and mass-produce replacement organs, cartilage or muscle. Bioengineer Ibrahim Ozbolat and his team at the University of Iowa have successfully used a 3D printer fitted with two robot arms to create tissue of two key types.

Until now, bioprinting has largely involved depositing a single type of human cell – like skin cells – onto a scaffold that is later dissolved. But the scaffold approach cannot produce 3D analogues of cartilage and muscle, for instance, which incorporate strong, fibrous cellular-material as well as individual cells of other types.

So Oxbolat’s team equipped a 3D printer with two robot arms so that it can simultaneously deposit filaments and cells. They fitted a nozzle to one arm and used it to create multilayer patterns with filaments of sodium alginate. The other arm populated the gaps between the filaments with cells that grow into cartilage.


The result was a 20-layer stack of tissue, 20 millimetres square, made of filaments and living cells, that did not require a scaffold.

Tissue issue

“A third or fourth arm could now be added, as on a robotics assembly line, with each depositing different components of tissue – whether it is blood vessels, connective tissue or organ specific tissue,” Ozbolat says.

Sheila MacNeil, a tissue engineer at the University of Sheffield’s Centre for Biomaterials and Tissue Engineering in the UK, says the idea has promise, but wonders about the strength of the tissue. “To me, filaments mean fibre with some mechanical integrity and, as these are gels of alginate, I suspect the mechanical integrity is not very high,” she says.

“However I could see the current system being a good experimental model for drug development, where having lots of replicated cells within a structure allows multiple dose responses to be tested.”

The centre’s engineering specialist, Patrick Smith, says multiple robot arms are key to this kind of technology. “Systems that allow multi-material deposition are the next step forward for additive manufacturing. And systems that can deposit combinations of functional materials in particular.”

Journal reference: Robotics and Computer Integrated Manufacturing, DOI: 10.1016/j.rcim.2013.10.005