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Skip to 0 minutes and 10 seconds So Johnson, we’re going to have to create a very complex 3D printed structure– one that replicates the shape that we see, the very complex shapes that we see in an ear– one that distributes the mechanical properties throughout that 3D printed ear structure. And then, of course, we need to be able to grow cartilage as well within that 3D structure. So how are we going to achieve that? Yes. So in order to create a complicated structure, we need a printer with multiple heads that loads in different bio-inks to do this purpose. So we have an ink that basically holds the cell together and protects it during the printing process. And that’s usually a hydrogel-based material.

Skip to 0 minutes and 50 seconds And then, we have a material that basically gives you the mechanical stability. So for example, in an ear structure, you need to be able to withstand certain contraction from the skin, as well as hold your glasses, for example. And so that material gives the mechanical stability. And the third material would be the sacrificial material. It’s unique in which the ear has a certain curvature. And in order to print that layer by layer, we need a sacrificial material underneath to hold the structure while it’s printing. It’s usually a gel-based material, or a material that is suitable to get rid of after the whole structure is printed. So for our case, it would usually be aqueous-based hydrogel.

Skip to 1 minute and 31 seconds So in a 37 degree incubator or through just washing with PBS or a cell culture media, it would just wash away and would not affect the other hydrogel that has cells incorporated in it. And so does that support material create basically a template into which you start to then print the material that will give you the structure? What the machine does, it will lay the support material first, create a template where it determines that it needs to have a certain angle. The second material then loads on. And then the third material then goes in between. So we have our sacrificial hydrogel. And that’s been printed.

Skip to 2 minutes and 9 seconds So what material do we use next in order to create the real replica of the ear shape and structure? For our mechanical stability, we use polycaprolactone, which is a thermoplastic and will melt extrudable material. That provides a lot of structural support. That also gives the compression strength that we use modelling as well to determine what’s the best scenario in terms of trying to replicate that ear. The most important would be the bio-ink, which is the ink that incorporates not only the cells, but growth factors as well. So we load that material into a syringe, and then lay it out either in between the PCL, or on top of the PCL layer by layer.

Skip to 2 minutes and 51 seconds So we have a support material as the base. We have the polycaprolactone that provides the shape and the mechanical properties. And then it’s another gel material that basically fills that interstitial volume which allows the cartilage to grow. Is that correct? That is correct. So the gel material protects the cell after implantation. So it gives the cartilage– which is mainly the stem cells or chondrocytes, in this case– time to mature. So after they mature, the gel then blends in with the normal tissue. And the tissue matures over time and creates its own extracellular matrix to provide stiffness to the implant.

Skip to 3 minutes and 30 seconds So it really does demonstrate the power of 3D printing in taking what we would consider now to be fairly conventional materials, but arranging them in an appropriate way to replicate shape, to distribute mechanical properties, and to facilitate cartilage regeneration, all because we can take simple materials and arrange them properly. That’s basically it. None of the human body parts are in simple arrangement. We need it to be arranged in a specific way. And 3D printing will help us to do that, to deposit cells or materials at particular locations. And that’s essentially what we’re trying to do.

Skip to 4 minutes and 7 seconds So the development of 3D printing technologies, in order to create a 3D printed ear, has required us to use many different types of 3D printing, starting with extrusion printing, so that we can replicate shape and mechanical properties. And now, looking at multi-head printing, so that we can introduce into that structure soft gel materials containing living cells that can subsequently develop into cartilage. Eventually, however, we need to build dedicated customised printing approaches to tackle challenges like 3D printed ears in the clinical environment. Each of these clinical projects requires an outcome that delivers that customised printing approach into an environment where it can be used reliably and reproducibly by clinical researchers, and eventually by clinical practitioners.

The fabrication

Structure complexities: Shape, mechanical properties, suitable to support multiple bio-inks

Printing techniques

Initially in week 1, we began considering how we would go about fabricating fingers on a hand; a wearable prosthetic. We considered the inclusion requirements in the STL file, we imported the data from that file into slicing and printing software which was coupled to the fused deposition machine printer. We considered placement on the build tray, touched on the differences between draft setting and fine settings in relation to final resolution and saw the necessity of scaffolding and support material to assist with overhanging components.

Throughout week 2, we shifted our focus to thinking about the fabrication process when creating an implant. Once again, we started with an STL file, but this time using Poly-jet processing on an inkjet printer using biocompatible materials. Once again supportive material was printed with the structure to ensure structural integrity. We saw the benefits of this process included being able to produce multiple prints of the same component within the one build tray, in one print run, under the same conditions.

Now in week 3, we consider how fabrication has advanced to include complexities such as printing with ink including cells (bioink), along with materials that support mechanical structure such as polycarbonate lactone, and a protective scaffold to ensure the structure as a whole such as hydrogels.

Your turn

Finally, you’ve identified a clinical need, considered the design necessary to suit this need, you’ve thought about the material that may be used to help print a suitable 3D structure. We would now like you to use this discussion space to consider how the fabrication process might work for your selected clinical need.

  • Would new technologies and methods need to be developed?
  • What complexities would need to be considered?

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This video is from the free online course:

Bioprinting: 3D Printing Body Parts

University of Wollongong