New project to build nano-thermometers could revolutionize temperature
imaging
Cheaper refrigerators? Stronger hip implants? A better understanding of
human disease? All of these could be possible

Date:
October 9, 2020
Source:
National Institute of Standards and Technology (NIST)
Summary:
Cheaper refrigerators? Stronger hip implants? A better understanding
of human disease? All of these could be possible and more, someday,
thanks to an ambitious new project.



FULL STORY ========================================================================== Cheaper refrigerators? Stronger hip implants? A better understanding
of human disease? All of these could be possible and more, someday,
thanks to an ambitious new project underway at the National Institute
of Standards and Technology (NIST).


==========================================================================
NIST researchers are in the early stages of a massive undertaking to
design and build a fleet of tiny ultra-sensitive thermometers. If they
succeed, their system will be the first to make real-time measurements
of temperature on the microscopic scale in an opaque 3D volume -- which
could include medical implants, refrigerators, and even the human body.

The project is called Thermal Magnetic Imaging and Control (Thermal
MagIC), and the researchers say it could revolutionize temperature
measurements in many fields: biology, medicine, chemical synthesis, refrigeration, the automotive industry, plastic production -- "pretty
much anywhere temperature plays a critical role," said NIST physicist
Cindi Dennis. "And that's everywhere." The NIST team has now finished
building its customized laboratory spaces for this unique project and
has begun the first major phase of the experiment.

Thermal MagIC will work by using nanometer-sized objects whose magnetic
signals change with temperature. The objects would be incorporated into
the liquids or solids being studied -- the melted plastic that might be
used as part of an artificial joint replacement, or the liquid coolant
being recirculated through a refrigerator. A remote sensing system would
then pick up these magnetic signals, meaning the system being studied
would be free from wires or other bulky external objects.

The final product could make temperature measurements that are 10 times
more precise than state-of-the-art techniques, acquired in one-tenth
the time in a volume 10,000 times smaller. This equates to measurements accurate to within 25 millikelvin (thousandths of a kelvin) in as
little as a tenth of a second, in a volume just a hundred micrometers (millionths of a meter) on a side. The measurements would be "traceable"
to the International System of Units (SI); in other words, its readings
could be accurately related to the fundamental definition of the kelvin,
the world's basic unit of temperature.



==========================================================================
The system aims to measure temperatures over the range from 200 to
400 kelvin (K), which is about -99 to 260 degrees Fahrenheit (F). This
would cover most potential applications -- at least the ones the Thermal
MagIC team envisions will be possible within the next 5 years. Dennis
and her colleagues see potential for a much larger temperature range, stretching from 4 K-600 K, which would encompass everything from
supercooled superconductors to molten lead. But that is not a part of
current development plans.

"This is a big enough sea change that we expect that if we can develop
it - - and we have confidence that we can -- other people will take it
and really run with it and do things that we currently can't imagine,"
Dennis said.

Potential applications are mostly in research and development, but Dennis
said the increase in knowledge would likely trickle down to a variety
of products, possibly including 3D printers, refrigerators, and medicines.

What Is It Good For? Whether it's the thermostat in your living room or
a high-precision standard instrument that scientists use for laboratory measurements, most thermometers used today can only measure relatively
big areas -- on a macroscopic as opposed to microscopic level. These conventional thermometers are also intrusive, requiring sensors to
penetrate the system being measured and to connect to a readout system
by bulky wires.



========================================================================== Infrared thermometers, such as the forehead instruments used at many
doctors' offices, are less intrusive. But they still only make macroscopic measurements and cannot see beneath surfaces.

Thermal MagIC should let scientists get around both these limitations,
Dennis said.

Engineers could use Thermal MagIC to study, for the first time, how
heat transfer occurs within different coolants on the microscale,
which could aid their quest to find cheaper, less energy-intensive refrigeration systems.

Doctors could use Thermal MagIC to study diseases, many of which are
associated with temperature increases -- a hallmark of inflammation --
in specific parts of the body.

And manufacturers could use the system to better control 3D printing
machines that melt plastic to build custom objects such as medical
implants and prostheses. Without the ability to measure temperature on the microscale, 3D printing developers are missing crucial information about
what's going on inside the plastic as it solidifies into an object. More knowledge could improve the strength and quality of 3D-printed materials someday, by giving engineers more control over the 3D printing process.

Giving It OOMMF The first step in making this new thermometry system is creating nano-sized magnets that will give off strong magnetic signals
in response to temperature changes. To keep particle concentrations as
low as possible, the magnets will need to be 10 times more sensitive to temperature changes than any objects that currently exist.

To get that kind of signal, Dennis said, researchers will likely need
to use multiple magnetic materials in each nano-object. A core of one
substance will be surrounded by other materials like the layers of
an onion.

The trouble is that there are practically endless combinations of
properties that can be tweaked, including the materials' composition,
size, shape, the number and thickness of the layers, or even the number
of materials. Going through all of these potential combinations and
testing each one for its effect on the object's temperature sensitivity
could take multiple lifetimes to accomplish.

To help them get there in months instead of decades, the team is turning
to sophisticated software: the Object Oriented MicroMagnetic Framework
(OOMMF), a widely used modeling program developed by NIST researchers
Mike Donahue and Don Porter.

The Thermal MagIC team will use this program to create a feedback
loop. NIST chemists Thomas Moffat, Angela Hight Walker and Adam
Biacchi will synthesize new nano-objects. Then Dennis and her team will characterize the objects' properties. And finally, Donahue will help them
feed that information into OOMMF, which will make predictions about what combinations of materials they should try next.

"We have some very promising results from the magnetic nano-objects side
of things, but we're not quite there yet," Dennis said.

Each Dog Is a Voxel So how do they measure the signals given out by tiny concentrations of nano- thermometers inside a 3D object in response to temperature changes? They do it with a machine called a magnetic particle imager (MPI), which surrounds the sample and measures a magnetic signal
coming off the nanoparticles.

Effectively, they measure changes to the magnetic signal coming off one
small volume of the sample, called a "voxel" -- basically a 3D pixel --
and then scan through the entire sample one voxel at a time.

But it's hard to focus a magnetic field, said NIST physicist Solomon
Woods. So they achieve their goal in reverse.

Consider a metaphor. Say you have a dog kennel, and you want to
measure how loud each individual dog is barking. But you only have one microphone. If multiple dogs are barking at once, your mic will pick up
all of that sound, but with only one mic you won't be able to distinguish
one dog's bark from another's.

However, if you could quiet each dog somehow -- perhaps by occupying its
mouth with a bone -- except for a single cocker spaniel in the corner,
then your mic would still be picking up all the sounds in the room,
but the only sound would be from the cocker spaniel.

In theory, you could do this with each dog in sequence -- first the
cocker spaniel, then the mastiff next to it, then the labradoodle next
in line -- each time leaving just one dog bone-free.

In this metaphor, each dog is a voxel.

Basically, the researchers max out the ability of all but one small volume
of their sample to respond to a magnetic field. (This is the equivalent
of stuffing each dog's mouth with a delicious bone.) Then, measuring
the change in magnetic signal from the entire sample effectively lets
you measure just that one little section.

MPI systems similar to this exist but are not sensitive enough to
measure the kind of tiny magnetic signal that would come from a small
change in temperature. The challenge for the NIST team is to boost the
signal significantly.

"Our instrumentation is very similar to MPI, but since we have to
measure temperature, not just measure the presence of a nano-object,
we essentially need to boost our signal-to-noise ratio over MPI by a
thousand or 10,000 times," Woods said.

They plan to boost the signal using state-of-the-art technologies. For
example, Woods may use superconducting quantum interference devices
(SQUIDs), cryogenic sensors that measure extremely subtle changes in
magnetic fields, or atomic magnetometers, which detect how energy levels
of atoms are changed by an external magnetic field. Woods is working on
which are best to use and how to integrate them into the detection system.

The final part of the project is making sure the measurements are
traceable to the SI, a project led by NIST physicist Wes Tew. That will
involve measuring the nano-thermometers' magnetic signals at different temperatures that are simultaneously being measured by standard
instruments.

Other key NIST team members include Thinh Bui, Eric Rus, Brianna Bosch
Correa, Mark Henn, Eduardo Correa and Klaus Quelhas.

Before finishing their new laboratory space, the researchers were able
to complete some important work. In a paper published last month in the International Journal on Magnetic Particle Imaging, the group reported
that they had found and tested a "promising" nanoparticle material made
of iron and cobalt, with temperature sensitivities that varied in a controllable way depending on how the team prepared the material. Adding
an appropriate shell material to encase this nanoparticle "core" would
bring the team closer to creating a working temperature-sensitive
nanoparticle for Thermal MagIC.

In the past few weeks, the researchers have made further progress testing combinations of materials for the nanoparticles.

"Despite the challenge of working during the pandemic, we have had some successes in our new labs," Woods said. "These achievements include our
first syntheses of multi-layer nanomagnetic systems for thermometry,
and ultra-stable magnetic temperature measurements using techniques
borrowed from atomic clock research."

========================================================================== Story Source: Materials provided by National_Institute_of_Standards_and_Technology_(NIST).

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. A.J. Biacchi, T.Q. Bui, C.L. Dennis, S.I. Woods, A.R. Hight Walker.

Design and engineering colloidal magnetic particles for nanoscale
thermometry. International Journal on Magnetic Particle Imaging,
September 2, 2020 DOI: 10.18416/ijmpi.2020.2009068 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201009162433.htm

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