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3D printing is an advancement that has infinite implementations. While the current limitations of the tech is crippling progress, someone came up with a genius plan.
You can pretty much 3D print anything these days: clothing, musical instruments, body parts, human stem cells, food, even a full replica of your unborn foetus (that’s one for the Christmas wish list!).
But despite their wizardry, commercial 3D printers do have their limits. Typically, 3D masterpieces are created when the printer spits out layer upon layer of filament, thus creating a solid shell. However, some clever engineers at the University of Illinois have actually developed a free-form 3D printer that can manufacture delicate and detailed scaffold-like structures. “Free-form” refers to the process whereby the printer nozzle essentially draws in mid-air while releasing the melted material, which then hardens into a stable structure. And in this instance, that melted material is not the traditional polymer filament but actually a water-soluble, glassy, biodegradable type of sugar, which is often found in throat lozenges, called “isomalt”.
Essentially, this printer transforms isomalt into an intricate but sturdy network of thin ribbons, producing impressively detailed, three-dimensional biological scaffolds, which can then house actual tissues while they grow. The sugar scaffolds then later dissolve, leaving behind a series of intersecting cylindrical tubes and tunnels, which can act similarly to blood vessels by transporting nutrients around the tissue. This is why the technology holds particular appeal for device manufacturers, cancer researchers and biomedical engineers.
Rohit Bhargava is a professor of bioengineering and the director of the Cancer Centre in Illinois. To the Illinois News Bureau he said, “This is a great way to create shapes around which we can pattern soft materials or grow cells and tissue, then the scaffold dissolves away. For example, one possible application is to grow tissue or study tumors in the lab. Cell cultures are usually done on flat dishes; that give us some characteristics of the cells, but it’s not a very dynamic way to look at how a system actually functions in the body. In the body, there are well-defined shapes, and shape and function are very closely related.”
Sugar alcohol isomalt was found to work most effectively for printing applications, as it is less prone to crystallisation or burning during the printing process. The key was then to build a printer that was precise enough in terms of nozzle measurement, appropriate temperature and sufficient speed to ensure the isomalt structures print smoothly but then harden into a stable structure. Of course, after the materials and the mechanics were sorted, the third consideration was computer science and working out exactly how to tell the printer to make what it is you need to be made. As Matthew Gelber, PhD graduate and author of the paper published in Additive Manufacturing, said, “How do you figure out the sequence to print all these intersecting filaments so it doesn’t collapse?” The solution arrived in the form of an algorithm to design scaffolds and map out printing pathways, which was devised when the Illinois team joined forces with Greg Hurst at Wolfram Research in Champaign.
Bhargava said the advantage that these free-form structures have over conventional 3D printing, is that they maintain their ability to create thin tubes with circular cross-sections; and when the sugar dissolves, a series of connected cylindrical tubes and tunnels remain, which can be used like blood vessels to transport nutrients in tissue, or to create channels in microfluidic devices. He also indicated the ability to make slight changes in the printer parameters, in order to precisely control the mechanical properties of each part of a structure, as another key advantage. He said, “For example, we printed a bunny. We could, in principle, change the mechanical properties of the tail of the bunny to be different from the back of the bunny, and yet be different from the ears. This is very important, biologically. In layer-by-layer printing, you have the same material and you’re depositing the same amount, so it’s very difficult to adjust the mechanical properties.”
“This printer is an example of engineering that has long-term implications for biological research,” he added. “This is fundamental engineering coming together with materials science and computer science to make a useful device for biomedical applications.”