3D printing

Engineers from the University of Illinois built a 3D printer that produces a delicate network of thin ribbons of hardened sugar alcohol, isomalt. These detailed biological structures are water-soluble, biodegradable glassy structures that could have multiple applications in biomedical engineering, cancer research, and device manufacturing.

3D printing is slowly entering every area of our lives. We are witnessing the emergence of fabricated pizzascoral reefsspace fabric, and even human corneas. Possibilities seem to be limitless. 3D printers capable of working with sugar already exist. Sugar’s unique ability to be melted down into a glass-like substance enables fabrication of tasty 3D-printed desserts. These same properties make it great for serious science too.

Ph.D. graduate Matthew Gelber and Rohit Bhargava, a professor of bioengineering and Director of the Cancer Center at Illinois, created a new kind of 3D printer. Their work was published in the journal Additive Manufacturing. Bhargava’s team worked with isomalt, a sugar substitute derived from beets and commonly used to make throat lozenges. After being melted down and printed, the sugar structures cool and solidify. A sturdy scaffold is produced and the structures can be used in biomedical engineering.

“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,” said Bhargava in TechXplore. “For example, one possible application is to grow tissue or study tumors in the lab.”

There are some tricky parts when printing sugar scaffolds for growing something as complicated as heart tissue. If too much pressure is applied the result is formless. It can burn or crystallize because of too much heat. Isomalt was chosen with purpose. It is less prone to crystallization than table sugar and resists discoloration when melted.

“Cell cultures are usually done on flat dishes. That gives 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,” said Bhargava.

For that reason, the team designed their free-form printer using very specific settings. They can control speed, temperature, and pressure with high precision. As the nozzle moves through space, the melted material hardens, leaving a sturdy structure behind. Like drawing in midair, they produce complex isomalt ribbons and tubes that resemble organic structures. By making slight changes in the printer parameters, they can even change the mechanical properties of each part of the structure.

“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,” Bhargava said. “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.”

After the tissue has fully grown around a scaffold, the sugar will simply dissolve and leave a series of inter-laced tubes and tunnels that can be used like blood vessels to transport nutrients. The research group hopes to develop coatings to control when and how fast the structures dissolve.

Although we are still a long way from using 3D printing to grow functional human organs or hydrogel-based medical devices, this technology is developing rapidly. The future of medicine could, it seems, be rather sweet.

Watch a video of isomalt sugar glass printing:

Learn more about making 3D printed sweets and our nutrition future in the video below:

By Andreja Gregoric, MSc