3D printed sugar offers sweet solution for tissue engineering, device
May 25, 2018
of Illinois engineers built a 3-D printer that offers a sweet solution
to making detailed structures that commercial 3-D printers can't: Rather
than a layer-upon-layer solid shell, it produces a delicate network of
thin ribbons of hardened isomalt, the type of sugar alcohol used to make
The water-soluble, biodegradable glassy sugar structures have multiple
applications in biomedical engineering, cancer research and device
"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 Rohit Bhargava, a professor of bioengineering and director of the
Cancer Center at Illinois. "For example, one possible application is to
grow tissue or study tumors in the lab. 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."
In a paper published in the journal Additive Manufacturing, the research
group described the materials and mechanics of free-form isomalt
printing. Free-form means that as the nozzle moves through space, the
melted material hardens, leaving a sturdy structure behind - like
drawing in midair.
Other types of sugar printing have been previously explored, but have
problems with the sugar burning or crystallizing, said Matthew Gelber,
the first author of the paper who recently graduated from Bhargava's
group with a Ph.D.
The Illinois team found that the sugar alcohol isomalt could work for
printing applications and is less prone to burning or crystallization.
Then they had to build a printer that would have the right combination
of mechanical details to print stable isomalt structures - the right
temperature, pressure to extrude it from the nozzle, diameter of the
nozzle, and speed to move it so it prints smoothly but then hardens into
a stable structure.
See a video of a bridge model being printed at https://youtu.be/kxpLZRfrmjE.
"After the materials and the mechanics, the third component was computer
science," Gelber said. "You have a design of a thing you want to make;
how do you tell the printer to make it? How do you figure out the
sequence to print all these intersecting filaments so it doesn't
The Illinois researchers partnered with Greg Hurst at Wolfram Research
in Champaign to create an algorithm to design scaffolds and map out
One advantage such free-form structures hold is their ability to make
thin tubes with circular cross-sections, something not possible with
conventional polymer 3-D printing, Bhargava said. When the sugar
dissolves, it leaves a series of connected cylindrical tubes and tunnels
that can be used like blood vessels to transport nutrients in tissue or
to create channels in microfluidic devices.
Another advantage is the ability to precisely control the mechanical
properties of each part of the structure by making slight changes in the
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."
Bhargava's group is already using the scaffolds in a variety of
microfluidic devices and cell cultures, and it is working to develop
coating for the scaffolds to control how quickly they dissolve. The
Additive Manufacturing paper is part of a series of publications based
on Gelber's thesis work that details how to build the printer and the
planning algorithms necessary to operate it, as the researchers hope
that others can use their models to build printers and explore various
applications for isomalt structures.
"This printer is an example of engineering that has long-term
implications for biological research," Bhargava said. "This is
fundamental engineering coming together with materials science and
computer science to make a useful device for biomedical applications."