Tech Briefs Magazine - April 2022 - 26

Manufacturing &
Prototyping
Full-Sized 3D-Bioprinted Heart Model
Surgeons can use the heart model as a tool for planning and practice.
Carnegie Mellon University, Pittsburgh, PA
A
team at Carnegie Mellon University
has created a full-sized 3D-bioprinted
human heart model using
the Freeform Reversible Em bedding
of Suspended Hydrogels (FRESH)
technique. The model, created from
MRI data using a specially built 3D
printer, realistically mimics the elasticity
of cardiac tissue and sutures.
The FRESH technique of 3D bioprinting
was invented to fill a demand
for 3D-printed soft polymers, which
lack the rigidity to stand unsupported
as in a normal print. FRESH 3D
printing uses a needle to inject bioink
into a bath of soft hydrogel,
which supports the object as it prints.
Once finished, a simple application of
heat causes the hydrogel to melt away,
leaving only the 3D-bioprinted object.
The major obstacle to achieving this
milestone was printing a human heart
at full scale. This necessitated the build
A completed 3D-bioprinted heart model. (Photo: CMU)
ing of a new 3D printer custom-made to
hold a gel support bath large enough to
print at the desired size as well as minor
software changes to maintain the speed
and fidelity of the print.
Major hospitals often have facilities
for 3D printing models of a patient's
body to help surgeons educate patients
and plan for the actual procedure;
however, these tissues and
organs can only be modeled in hard
plastic or rubber. The team's heart
is made from a soft, natural polymer
called alginate, giving it properties
similar to real cardiac tissue. For
surgeons, this enables the creation
of models that can cut, suture, and
be manipulated in ways similar to a
real heart. The immediate goal is to
begin working with surgeons and
clinicians to fine tune their technique
and ensure it's ready for the
hospital setting.
Surgeons can manipulate the model
and have it actually respond like real tissue,
so that when they get into the operating
site, they've got an additional layer
of realistic practice in that setting.
For more information, contact E. Forney
at eforney@cmu.edu; 412-268-1422.
Method Recycles Facemasks into Roads to Combat
COVID-Generated Waste
Making one kilometer of a two-lane road would use up about three million masks.
RMIT University, Melbourne, Australia
A
new road-making material is a
mix of shredded single-use facemasks
and processed building rubble
that meets civil engineering safety
standards. The use of personal protective
equipment (PPE) increased
dramatically during the COVID-19
pandemic, with an estimated 6.8 billion
disposable facemasks being used
across the globe each day.
Analysis shows the facemasks help
to add stiffness and strength to the
final product, which is designed to
be used for base layers of roads and
pavements. Roads are made of four
layers: subgrade, base, sub-base, and
asphalt on top. All the layers must be
both strong and flexible to withstand
the pressures of heavy vehicles and prevent
cracking. Processed building rubble
- known as recycled concrete aggregate
(RCA) - can potentially be used on its
own for the three base layers.
26
tion waste. Construction, renovation,
and demolition account for
about half the waste produced
annually worldwide.
A sample of the recycled road-making material, which
blends shredded single-use facemasks with processed
building rubble. (Photo: RMIT University)
The researchers found adding
shredded facemasks to RCA enhances
the material while simultaneously addressing
environmental challenges on
two fronts: PPE disposal and construcwww.techbriefs.com
The
researchers identified an
optimal mixture of 1 percent
shredded facemasks to 99 percent
RCA that delivers on strength
while maintaining good cohesion
between the two materials.
The mixture performs well when
tested for stress, acid, and water
resistance as well as strength, deformation,
and dynamic properties,
meeting all the relevant civil
engineering specifications.
In related work, the researchers
also investigated the use of shredded
disposable facemasks as an aggregate
material for making concrete, with promising
preliminary findings.
For more information, contact RMIT news
at news@rmit.edu.au; +61 439 704 077.
Tech Briefs, April 2022
TB Manufacturing Prototyping 0422_1.indd 26
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Tech Briefs Magazine - April 2022

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