September is the month for September. Vitro3D The company was recognized for its potential with Volumetric Additive Manufacturing technology.
This technology was developed originally at the University of Colorado Boulder In an attempt to overcome a number challenges associated with photopolymer 3-D printing. The company raised 1.3 million dollars in seed funding for its commercialisation target of 2025.
Sam Davies, TCT Group’s Content Manager, sat down recently with Vitro3D’s CEO Camila Uzcategui PhD to learn more. This was part of a podcast episode, Additive Insight, that has not yet been released.
Vitro3D frequently talks about addressing limitations of photopolymer 3-D printing. What are these limitations, and what was the key to addressing those?
CU: By the time I finished my degree [from University of Colorado Boulder]I am a member of the [Bob] McCleod Lab was a postdoc at the time, and we began to shift our focus from stereolithography and digital light production to volumetric additive manufacturing in order to better understand how it could be used to create these complex parts, and to explore new applications. When we did that, we realized that volumetric manufacturing could solve many of the problems we faced when considering photopolymer-based additive manufacturing. For example, it was difficult to print parts that were complex due to the high viscosity of some materials. In the early days of my PhD, when I was 3D printing surgical scaffolds that we implanted in animal models, it took me 20 to 30 minutes to complete one 5 millimetres by 5 millimetres by 2 millimetres-sized part. And then [when] When I first started to work on this technology, I was working with volumetrics. We could print something similar in only a few moments.
Can you tell us all you know about Volumetric Additive Manufacturing?
CU: A CAT scan is the best way I can describe volumetric additive manufacturing. So, [with a CAT scan] If you enter a machine with a circular design, it will take pictures of you from different angles by using a light source. This machine takes pictures from all different angles. Then, it uses a computer algorithm to combine the images to form a 3D virtual image. This is how the CAT scans are obtained and a virtual 3D image of the inside of the human body can be created. We use an inverse CAT scanner as the basis of our volumetric additive manufacturing. Instead of taking pictures from different angles, we deconstruct a 3D object into the various angles that comprise that part.
We say the magic lies in the software because instead of using a standard slicer, which slices a virtual three-dimensional object into two-dimensional slices, we use a robust algorithm, which takes the virtual three-dimensional object and deconstructs it into different angles. This algorithm then incorporates the material properties and projects a two-dimensional image from each angle onto the volume of photopolymerizable acrylic. Then, when the intensities are overlapping, and where they are highest, only those regions will go from liquid into solid, and undergo photopolymerisation.
I understand that one of the key elements to Vitro3D’s VAM technology is the speed. How has Vitro3D achieved rapid printing without compromising accuracy or resolution?
A volumetric additive manufacturing or 3D printing is one of the most important aspects. Our ability to materialise a part at once is so amazing. Because the process is so effective, and because it allows us to convert liquids to solids through photopolymerization by reaching a certain amount of energy, we can materialise a whole part at once rather than layer by layer. It is not only faster but also allows for new capabilities such as printing around an existing object, or printing a first part then printing around it in a secondary procedure.
Could you tell me what light source or heat source you use in this process. What is different about that heat source than, say, a conventional photopolymer printing technology, if anything?
Yeah, so the main difference in our case is that rather than wanting to photopolymerise a small layer of material, which is usually how layer by layer 3D printing methods work in the photopolymer space, we’re instead wanting to get as much light through the volume of our resin as we possibly can. This means that the light on the sample plane should be collimated, which means that the light will not change much through the volume. So, what that means is that we have to use very ingenious optical designs to ensure that we understand where the focus is of our two dimensional projection and ensuring that our depth of focus is as large as it can possibly be.
How do you get the part from its initial stage to the final stage after, I suppose, the post-processing?
We use the same solvent wash and post cure as every other 3D photopolymer printing method. Because we don’t need support structures because we print directly onto a volume, we can automate our post-processing. In other words, instead of having to take the part out of the printer and place it in a solvent-wash, then transfer it to a curing oven to cure it, we could do the whole process within our proprietary cartridges. This would allow us to 3D print a structure in the cartridge and then remove any unreacted resin with a solvent-wash, before performing a light-based post cure.
Volumetric post-curing works well because it is based on light. We do not need photoabsorbers. We don’t need photoabsorbers, so our post cure step is more efficient because we aren’t worried about the “candy shell” effect. If you 3D print a part layer by layer, and only put it through the photo-based post curing process, the cure will only be at the edges. This is what we call the candy shell effect. This is when heat post-processing steps are used for different chemistries or standard chemistries. In our case, however, the post-cure with light is very effective because we don’t have photoabsorbers.
What kind of material are you currently able to work with?
We can process many different materials, very similar to any other additive, photopolymerisation technology. Our main limitation is transparency. We want to make sure that the light can get through as much of the volume as possible, since we’re using a volumetric approach. It is important to always ensure that the material used is transparent to wavelengths. We’ve used materials ranging from soft hydrogels to stiff urethane matrixes with secondary materials for optical applications. What’s so amazing about this technology is not only that it can cover a wide range of viscosities but also that we can access new applications with other technologies that are limited by viscosity.
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