The Fascination of Technology The Ear from A 3D Printer 

Related Vendors

FAULHABER Drive Systems

Wuxi InfiMotion Technology Co., Ltd.

In our "Fascinating technology" section, we present impressive research and development projects to design engineers every week. Today: an artificial ear created from human ear cartilage cells and bio-ink in a 3D printer.

Time and again, people lose part or all of an ear in fires and accidents. Some children also suffer from a congenital malformation of the outer ear. This so-called microtia affects around one to four in 10,000 children. To date, reconstruction with the body's own rib cartilage is considered the standard. However, the reconstructed ear is often stiffer than a natural one. A challenge for researchers. For over thirty years, researchers have been trying to create an ear in the laboratory from living cell material from patients. Back in 2016, ETH Professor Marcy Zenobi-Wong's team surprised everyone with an ear from a 3D printer. Now researchers from ETH Zurich, the Friedrich Miescher Institute in Basel and Lucerne Cantonal Hospital have taken another important step towards their goal. They have been able to produce elastic ear cartilage from human ear cartilage cells in the laboratory, the mechanical properties of which come close to those of natural tissue. The artificial cartilage is as stable as a real ear and retained its shape and elasticity in the animal model even after six weeks.

From the Fabric Piece to the Printed Ear

As starting material, the researchers obtained cells from small pieces of cartilage left over from operations to correct the shape of the ear. One hundred thousand cells can initially be isolated from a small piece of tissue about 0.12 inches (3 millimetres) in diameter. However, several hundred million are needed for a printed ear. The researchers therefore allowed the cells to continue growing in a special nutrient solution in the laboratory. To ensure that the tissue matures evenly, the researchers also developed a special culture environment so that the inside of the printed ear is also supplied with sufficient nutrients and oxygen. The researchers then embedded the multiplied cells in a so-called bio-ink, a gel-like material that serves as a carrier. Using a 3D printer, they formed ear structures from this. Immediately after printing, the tissue was still very soft. "The decisive factor is not just what you put in, but how the tissue can develop," explains Philipp Fisch, first author of the study recently published in the journal Advanced Functional Materials and research associate in ETH Professor Marcy Zenobi-Wong's Tissue Technology and Biofabrication group. The printed ears therefore matured for several weeks in an incubator and were continuously supplied with nutrients. The aim was to produce type II collagen, elastin and glycosaminoglycans—sugar-like molecules that bind water and contribute to the strength of the cartilage.

Mechanical Properties Close to Natural Cartilage

A combination of four factors was crucial to their success, says Fisch: "We optimized cell proliferation, adapted the material properties, increased cell density and better controlled the maturation environment." After around nine weeks of pre-maturation in the laboratory, the researchers implanted the ear constructs under the skin of rats. There they observed the tissue over several weeks. The result: the shape remained stable after six weeks and the mechanical properties were close to those of natural cartilage. "Despite the great success, the not yet fully matured elastin remains a challenge for us," says Fisch. "We see changes in the tissue. This clearly shows us that we need to stabilize it further." There is great interest in artificial ear cartilage. "As soon as the study was published, I received a message from parents of a child with microtia," says Fisch. They wanted to know how far the research had progressed and when clinical trials could be expected. Fisch remains cautious: "If everything goes well, we will hopefully find the blueprint for the elastin network within the next five years." This will be followed by clinical trials, structured testing procedures and formal approval processes. Only when these regulatory hurdles have been overcome can the artificial ear cartilage find its way from the laboratory to the clinic.

Additive manufacturing

Basic knowledge 3D printing