How to print a robot from scratch: Combining liquids, solids could lead
to faster, more flexible 3D creations

Date:
April 18, 2022
Source:
University of Colorado at Boulder
Summary:
Engineers have developed a new way to 3D-print liquid and solid
materials together, potentially leading to more dynamic and useful
products -- from robots to wearable electronic devices.



FULL STORY ========================================================================== Imagine a future in which you could 3D-print an entire robot or stretchy, electronic medical device with the press of a button -- no tedious hours
spent assembling parts by hand.


==========================================================================
That possibility may be closer than ever thanks to a recent advancement
in 3D- printing technology led by engineers at the University of
Colorado Boulder. In a new study, the team lays out a strategy for
using currently-available printers to create materials that meld solid
and liquid components -- a tricky feat if you don't want your robot
to collapse.

"I think there's a future where we could, for example, fabricate a
complete system like a robot using this process," said Robert MacCurdy,
senior author of the study and assistant professor in the Paul M. Rady Department of Mechanical Engineering.

MacCurdy, along with doctoral students Brandon Hayes and Travis
Hainsworth, published their results April 14 in the journal Additive Manufacturing.

3D printers have long been the province of hobbyists and researchers
working in labs. They're pretty good at making plastic dinosaurs or
individual parts for machines, such as gears or joints. But MacCurdy
believes that they can do a lot more: By mixing solids and liquids,
3D printers could churn out devices that are more flexible, dynamic and potentially more useful. They include wearable electronic devices with
wires made of liquid contained within solid substrates, or even models
that mimic the squishiness of real human organs.

The engineer compares the advancement to traditional printers that print
in color, not just black-and-white.



========================================================================== "Color printers combine a small number of primary colors to create a rich
range of images," MaCurdy said. "The same is true with materials. If
you have a printer that can use multiple kinds of materials, you can
combine them in new ways and create a much broader range of mechanical properties." Empty space To understand those properties, it helps
to compare 3D printers to the normal printers in your office. Paper
printers create an image by laying down liquid inks in thousands of flat pixels. Inkjet 3D printers, in contrast, use a printhead to drop tiny
beads of fluid, called "voxels" (a mash-up of "volume" and "pixel"),
one on top of the other.

"Very soon after those droplets are deposited, they are exposed to a
bright, ultraviolet light," MacCurdy said. "The curable liquids convert
into solids within a second or less." But, he added, there are many cases
in which you might want those liquids to stay liquid. Some engineers,
for example, use liquids or waxes to create tiny channels within their
solid materials, which they then empty out at a later point. It's a bit
like how drips of water can carve out an underground cavern.



========================================================================== Engineers have come up with ways to make those kinds of empty spaces
in 3D- printed parts, but it usually takes a lot of time and effort to
clean them. The channels also have to stay relatively simple.

MacCurdy and his colleagues decided to find a way around those limitations
- - better understanding the conditions that would allow engineers to
print solid and liquid materials at the same time.

Liquid courage The researchers first designed a series of computer
simulations that probed the physics of printing different kinds of
materials next to each other. One of the big problems, MacCurdy said is:
How can you keep your droplets of solid materials from mixing into the
liquid materials, even when the droplets of solid material are printed
directly on top of the liquid droplets? "We found that the surface
tension of a liquid can be used to support solid material, but it is
helpful to pick a liquid material that is more dense than the solid
material -- the same physics that allow oil to float on top of water,"
Hayes said.

Next, the researchers experimented with a real 3D printer in the lab. They loaded the printer up with a curable polymer, or plastic (the solid),
and with a standard cleaning solution (the liquid). Their creations were impressive: The group was able to 3D-print twisting loops of liquid and
a complex network of channels not unlike the branching pathways in a
human lung.

"Both structures would have been nearly impossible to make through
previous approaches," Hainsworth said.

MacCurdy also recently joined a team of researchers from CU Boulder
and the CU Anschutz Medical Campus who are developing ways to 3D-print realistic models of human tissue. Doctors could use these models to
practice for procedures and make diagnoses. The project will employ
MacCurdy's liquid-solid approach among other tools.

"We hope that our results will make multimaterial inkjet 3D printing
using liquids and solids more accessible to researchers and enthusiasts
around the world," he said.


========================================================================== Story Source: Materials provided by
University_of_Colorado_at_Boulder. Original written by Daniel
Strain. Note: Content may be edited for style and length.


========================================================================== Related Multimedia:
* 3D-printed_network_of_capillaries_and_a_spiral ========================================================================== Journal Reference:
1. Brandon Hayes, Travis Hainsworth, Robert MacCurdy. Liquid-solid co-
printing of multi-material 3D fluidic devices via material jetting.

Additive Manufacturing, 2022; 102785 DOI:
10.1016/j.addma.2022.102785 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220418164923.htm

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