Medical Design Briefs - May 2024 - 26

Researchers 3D Print Key Components for a Point-ofCare
Mass Spectrometer
The low-cost hardware
could enable an affordable,
in-home device for
health monitoring.
MIT
Cambridge, MA
Mass spectrometry, a technique that can
precisely identify the chemical components
of a sample, could be used to monitor the
health of people who suffer from chronic
illnesses. For instance, a mass spectrometer
can measure hormone levels in the
blood of someone with hypothyroidism.
But mass spectrometers can cost several
hundred thousand dollars, so these expensive
machines are typically confined to laboratories
where blood samples must be
sent for testing. This inefficient process can
make managing a chronic disease especially
challenging.
" Our big vision is to make mass spectrometry
local. For someone who has a
chronic disease that requires constant
monitoring, they could have something
the size of a shoebox that they could use to
do this test at home. For that to happen,
the hardware has to be inexpensive, " says
Luis Fernando Velásquez-García, a principal
research scientist in MIT's Microsystems
Technology Laboratories (MTL).
He and his collaborators have taken a big
step in that direction by 3D printing a lowcost
ionizer - a critical component of all
mass spectrometers - that performs twice
as well as its state-of-the-art counterparts.
Their device, which is only a few centimeters
in size, can be manufactured at
scale in batches and then incorporated
into a mass spectrometer using efficient,
pick-and-place robotic assembly methods.
Such mass production would make it
cheaper than typical ionizers that often require
manual labor, need expensive hardware
to interface with the mass spectrometer,
or must be built in a semiconductor
clean room.
By 3D printing the device instead, the researchers
were able to precisely control its
shape and utilize special materials that
helped boost its performance.
" This is a do-it-yourself approach to
making an ionizer, but it is not a contrap26
5
mm
1cm
MIT researchers have 3D printed a miniature ionizer, which is a key component of a mass spectrometer. The new
miniature ionizer could someday enable an affordable, in-home mass spectrometer for health monitoring. Pictured
are parts of the new device, including a green printed circuit board (PCB) with orange casing on top. Under the
casing is a black rectangle where the electrospray emitter is located. (Credit: MIT)
tion held together with duct tape or a
poor man's version of the device. At the
end of the day, it works better than devices
made using expensive processes
and specialized instruments, and anyone
can be empowered to make it, " says
Velásquez-García, senior author of a paper
on the ionizer.
He wrote the paper with lead author
Alex Kachkine, a mechanical engineering
graduate student. The research is published
in the Journal of the American Association
for Mass Spectrometry.
n Low-Cost Hardware
Mass spectrometers identify the contents
of a sample by sorting charged particles,
called ions, based on their mass-tocharge
ratio. Since molecules in blood
don't have an electric charge, an ionizer
is used to give them a charge before they
are analyzed.
Most liquid ionizers do this using electrospray,
which involves applying a high
voltage to a liquid sample and then firing a
thin jet of charged particles into the mass
spectrometer. The more ionized particles
in the spray, the more accurate the measurements
will be.
The MIT researchers used 3D printing,
along with some clever optimizations, to
produce a low-cost electrospray emitter
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that outperformed state-of-the-art mass
spectrometry ionizer versions.
They fabricated the emitter from metal
using binder jetting, a 3D printing process
in which a blanket of powdered material is
showered with a polymer-based glue squirted
through tiny nozzles to build an object
layer by layer. The finished object is heated
in an oven to evaporate the glue and then
consolidate the object from a bed of powder
that surrounds it.
" The process sounds complicated, but it
is one of the original 3D printing methods,
and it is highly precise and very effective, "
Velásquez-García says.
Then, the printed emitters undergo an
electropolishing step that sharpens it. Finally,
each device is coated in zinc oxide
nanowires which give the emitter a level of
porosity that enables it to effectively filter
and transport liquids.
n Thinking Outside the Box
One possible problem that impacts electrospray
emitters is the evaporation that
can occur to the liquid sample during operation.
The solvent might vaporize and
clog the emitter, so engineers typically design
emitters to limit evaporation.
Through modeling confirmed by experiments,
the MIT team realized they
could use evaporation to their advanMedical
Design Briefs, May 2024

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Medical Design Briefs - May 2024

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