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Glaucoma: Material selection

Printing techniques including the material and the type of printer are discussed.
Michael Coote has just told us about the need to design and to fabricate better implants to treat glaucoma. Implantation into the eye will require the materials to have very specific properties. The mechanical properties will be important to be compatible with that environment. So also will the chemical and biological properties to ensure biocompatibility. So let’s talk to Steve about what types of materials might be commercially available that meet those needs. So Gordon, we have a limited number of commercial biocompatible materials. They’re generally coupled with a specific 3D printing technology.
So in the case of this sort of an example, where we need high resolution, high detailed components with good-quality surface finish, we have to look towards an inkjet-based type technology, an example of that being PolyJet technology, where we’re putting down layers of UV-curable resin. And one of those particular materials that that particular company have is MED610. It’s a biocompatible implantable material for short-term implantation. We can achieve really high layer resolution. Gets down as far as 16 microns. And that enables us to get the small internal features that we need in a complex component like this. Small features like internal tubing, recesses that are 700 microns in diameter are easily achieved.
So the choice of materials and fabrication method here are not just dependent on the environment in which they’re to be used, but the actual resolution that’s required in the final device. Absolutely. The resolution is key. We have to be comparable to the conventional injection-molded component. And with PolyJet type technologies or inkjet-based type technologies, we are able to achieve those fine surface resolutions.
So this is a glaucoma implant design here. You can see the two channels in here that are used for the inlets or outlets. It’s about six millimetres in diameter. It’s planned to be fabricated using a MED610 material, which is biocompatible. It’s going to be made using a PolyJet process on an inkjet printer. Out of this photo cube of biocompatible material, 16 microns per layer. From here, we’re going to export an STL file, which is a mesh. We can then pass that into some proprietary 3D printing software, which will then slice the model into its respective layers and send it through to the printer. Once we get it out of the printer, it will be encapsulated in support material.
We can remove this support material using an abrasive process or a mechanical one, where we water-jet away the excess support material. From there, we can sterilise the part and send it off to our collaborators. So the key benefit that 3D printing allows us in this project is that we can make multiple different iterations of the same component or variants of the same component within the one build tray. That means we can have a range of different components all produced at the same time under the same conditions, cleaned here, then processed and sterilised with our colleagues for final implantation. We can then run simultaneous experiments, where we put different variants of the implant in different animals.
We can’t undertake that readily with conventional machining tools and conventional production methods, where we would have to have an individual mould for each one of the different designs.
3D printing broadens the horizon of what it is possible to fabricate.
Once the engineer understands the limitations of the particular printer (including build volume, lateral resolution, layer thickness and overhang support) they can be confident that almost any shape can be created.
Intricate internal architectures can be created, without joints or glue. Multi-component parts can be fabricated, in one step, in a ‘pre-assembled’ state. 3D printing allows for the creation of structures which would not be possible by other means.
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Bioprinting: 3D Printing Body Parts

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