Medical Design Briefs - June 2022 - 25

challenge in the building of microscale
channels, " Chen says.
" This is the first time we've been able
to print something where the channel
height is at the 10 µm level; and we can
control it really accurately, to an error of
plus or minus one micron. This is something
that has never been done before,
so this is a breakthrough in the 3D printing
of small channels, " he says.
Vat photopolymerization makes use of
a vat filled with liquid photopolymer resin,
out of which a printed item is constructed
layer by layer. Ultraviolet light is
then flashed onto the object, curing and
hardening the resin at each layer level.
As this happens, a build platform moves
the printed item up or down so additional
layers can be built onto it.
But when it comes to microfluidic devices,
vat photopolymerization has some
disadvantages in the creation of the tiny
wells and channels that are required on
the chip. The UV light source often penetrates
deeply in the residual liquid resin,
curing and solidifying material within
the walls of the device's channels, which
would clog the finished device.
" When you project the light, ideally,
you only want to cure one layer of the
channel wall and leave the liquid resin
inside the channel untouched; but it's
hard to control the curing depth, as we
are trying to target something that is
only a 10 µm gap, " Chen says.
He says that current commercial processes
only allowed for the creation of a
channel height at the 100 µm level with
poor accuracy control, due to the fact
that the light penetrates a cured layer
too deeply, unless you are using an
opaque resin that doesn't allow as much
light penetration.
" But with a microfluidic channel, typically
you want to observe something
under microscope, and if it's opaque,
you cannot see the material inside, so
we need to use a transparent resin, "
Chen says.
In order to accurately create channels
in clear resin at a microscale level suitable
for microfluidic devices, the team
developed a unique auxiliary platform
that moves between the light source and
the printed device, blocking the light
from solidifying the liquid within the
walls of a channel, so that the channel
roof can then be added separately to the
top of the device. The residual resin that
remains in the channel would still be in
a liquid state and can then be flushed
out after the printing process to form
the channel space.
The new research using the auxiliary
platform is demonstrated in this video
from the USC Viterbi research team.
" There are so many applications for
microfluidic channels. You can flow a
blood sample through the channel,
mixing it with other chemicals so you
can, for example, detect whether you
have COVID or high blood sugar levels, "
Chen says.
He says the new 3D printing platform,
with its microscale channels, allowed for
other applications, such as particle sorting.
A particle sorter is a type of microfluidic
chip that makes use of different sized
chambers that can separate different sized
particles. This could offer significant benefits
to cancer detection and research.
" Tumor cells are slightly bigger than
normal cells, which are around 20 µm.
Tumor cells could be over 100 µm, "
Chen says. " Right now, we use biopsies to
check for cancer cells; cutting organ or
tissue from a patient to reveal a mix of
healthy cells and tumor cells. Instead, we
could use simple microfluidic devices to
flow (the sample) through channels with
accurately printed heights to separate
cells into different sizes so we don't allow
those healthy cells to interfere with our
detection. "
Chen says the research team was now
in the process of filing a patent application
for the new 3D printing method
and is seeking collaboration to commercialize
the fabrication technique for
medical testing devices.
This article was written by Greta Harrison,
USC. For more information, visit http://info.
hotims.com/82322-373. A video of the technology
is available at https://www.youtube.
com/watch?v=bmbMU-z5xyA&t=14s.
Smartphone-Powered Microchip Enables At-Home
Medical Diagnostic Testing
The new technology could
make at-home diagnosis of
diseases faster and more
affordable.
University of Minnesota
Minneapolis, MN
A research team has developed a new microfluidic
chip for diagnosing diseases that
uses a minimal number of components and
can be powered wirelessly by a smartphone.
The University of Minnesota - Twin Cities
innovation opens the door for faster and
more affordable at-home medical testing.
Microfluidics involves the study and
manipulation of liquids at a very small
Medical Design Briefs, June 2022
Cov
MDB Tech Briefs 0622_1.indd 25
scale. One of the most popular applications
in the field is developing " lab-on-achip "
technology, or the ability to create
devices that can diagnose diseases from a
very small biological sample, blood, or
urine, for example.
Scientists already have portable devices
for diagnosing some conditions
- rapid COVID-19 antigen tests, for
one. However, a big roadblock to engineering
more sophisticated diagnostic
chips that could, for example,
identify the specific strain of
COVID-19 or measure biomarkers like
glucose or cholesterol, is the fact that
they need so many moving parts.
Chips like these would require materiwww.medicaldesignbriefs.com
ToC
5/25/22
2:50 PM
als to seal the liquid inside, pumps and
tubing to manipulate the liquid, and
wires to activate those pumps-all materials
that are difficult to scale down
to the micro level. Researchers at the
University of Minnesota Twin Cities
were able to create a microfluidic device
that functions without all of those
bulky components.
" Researchers have been extremely successful
when it comes to electronic device
scaling, but the ability to handle liquid
samples has not kept up, " says
Sang-Hyun Oh, a professor in the University
of Minnesota Twin Cities department
of electrical and computer engineering
and senior author of the study.
25
http://info.hotims.com/82322-373 https://www.youtube.com/watch?v=bmbMU-z5xyA&t=14s http://www.medicaldesignbriefs.com
Medical Design Briefs - June 2022

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