It may be true that seeing is believing, but sometimes hearing can be
better.
Case in point: Two brothers in a Rice University laboratory heard something
unusual while making graphene. Ultimately, they determined the sound itself
could give them valuable data about the product.
The brothers, John Li, a Rice alumnus now studying at Stanford University,
and Victor Li, then a high school student in New York and now a freshman at
the Massachusetts Institute of Technology, are co-lead authors of a paper
that describes the real-time analysis of laser-induced graphene (LIG)
production through sound.
The brothers were working in the lab of Rice chemist James Tour when they
came up with their hypothesis and presented it at a group meeting.
"Professor Tour said, "It is interesting," and told us to pursue it as a
potential project," John Li recalled.
The results, which appear in Advanced Functional Materials, describe a
simple acoustic signal processing scheme that analyzes LIG in real time to
determine its form and quality.
LIG, introduced by the Tour lab in 2014, makes layers of interconnected
graphene sheets by heating the top of a thin polymer sheet to 2,500 degrees
Celsius (4,532 degrees Fahrenheit), leaving only carbon atoms behind. The
technique has since been applied to making graphene from other feedstock,
even food.
"Under different conditions, we hear different sounds because different
processes are occurring," John said. "So if we hear variations during the
synthesis, we'd be able to detect different materials being formed."
He said audio analysis allows for "far greater quality control capabilities
that are orders of magnitude faster than characterization of laser-induced
graphene by microscopy techniques.
"In materials analysis, there are often tradeoffs between cost, speed,
scalability, accuracy and precision, especially in terms of how much
material you can systematically process," John said. "What we have here
allows us to efficiently scale the throughput of our analytical capabilities
to the entire amount of material we're trying to synthesize in a robust
manner."
John invited his younger brother to Houston, knowing his expertise would be
a plus in the lab. "We have complementary skill sets almost by design, where
I avoid specializing in the things that he knows very well, and likewise, he
avoids areas that I know very well," he said. "So we form a very solid team.
"Basically, I made the connection that the right sounds correspond to the
right product, and he made the connection that the different sounds
corresponded to different products," he said. "Also, he is much stronger
than I am at certain computational techniques, whereas I'm primarily an
experimentalist."
A small, $31 microphone from Amazon taped to the laser head and attached to
a cellphone inside the laser cabinet picks up the audio for analysis.
"The brothers converted the sound pattern through a mathematical technique
called a Fast Fourier transform, so they could get numerical data from the
sound data," Tour said. "Through some mathematical computations, that data
can be a near-instant analytical tool to assess the product type and
purity."
John Li said the sounds emitted "provide information on the relaxation of
the energy input when the laser hits the sample and gets absorbed,
transmitted, scattered, reflected or just in general converted into
different types of energy. That allows us to get local information on
properties of the graphene's microstructure, morphology and nanoscale
characteristics."
Tour remains impressed by their ingenuity.
"What these brothers came up with is amazing," he said. "They are hearing
the sounds of synthesis as it is performed, and from that they can determine
product type and quality near-instantaneously. This could be an important
approach during synthesis to guide manufacturing parameters."
He said sound analysis could contribute to a number of manufacturing
processes, including his own lab's flash Joule heating, a method to make
graphene and other materials from waste products, as well as sintering,
phase engineering, strain engineering, chemical vapor deposition,
combustion, annealing, laser-cutting, gas evolution, distillation and more.
"Between John's experimental expertise and Victor's mathematical talent, the
family team is formidable," Tour said. "My greatest joy is to provide an
atmosphere where young minds can create and flourish, and in this case, they
demonstrated expertise way beyond their years, John being only 19 and Victor
17 at the time of their discovery."
Co-authors of the paper are Rice graduate students Jacob Beckham and Weiyin
Chen, postdoctoral researcher Bing Deng, alumnus Duy Luong and research
scientist Carter Kittrell. Tour is the T.T. and W.F. Chao Chair in Chemistry
as well as a professor of computer science and of materials science and
nanoengineering.
Reference:
Victor D. Li et al, Sounds of Synthesis: Acoustic Real‐Time Analysis of
Laser‐Induced Graphene, Advanced Functional Materials (2022).
DOI: 10.1002/adfm.202110198
Tags:
Physics