Fingertip-sized chip replaces bulky laboratory equipment. An infrared sensor has been developed that analyzes the content of liquids within the fraction of a second.
From: Vienna University of Technology
August 30. 2022 -- In
analytical chemistry, it is often necessary to accurately monitor the
concentration change of certain substances in liquids on a time scale of
seconds. Especially in the pharmaceutical industry, such measurements need to
be extremely sensitive and reliable.
A new type of sensor
has been developed at TU Wien which is highly suitable for this task and
combines several important advantages in a unique way: based on customized
infrared technology, it is significantly more sensitive than previous standard
devices. Moreover, it can be used for a wide range of molecule concentrations
and it can operate directly in the liquid. This is the consequence of its
chemical robustness and thus provides data in real time, i.e. within fractions
of a second. These results have now been published in the scientific
journal Nature Communications.
Different molecules
absorb different wavelengths
"To measure the
concentration of molecules, we use radiation in the mid-infrared spectral
range," says Borislav Hinkov, head of the research project from the
Institute of Solid State Electronics at TU Wien. This is a well-known
technique: molecules absorb specific wavelengths in the mid-infrared range,
while other wavelengths are transmitted without attenuation. Thus, different
molecules have their very specific "infrared fingerprint." By
accurately measuring the wavelength-dependent absorption strength profile, it
is possible to determine the concentration of a particular molecule in the
sample at any given time.
Infrared spectroscopy
has routinely been used in gas sensing for a long time. The new achievement of
the team at TU Wien is the implementation of this technology on a
fingertip-sized sensor chip, which is specifically suitable for liquid sensing.
Developing such a sensor was a technological as well as an analytical
challenge, because liquids absorb infrared radiation much stronger than gases.
The compact liquid sensor was realized in collaboration with Benedikt Schwarz
from the Institute of Solid State Electronics and fabricated in the Centre for
Micro- and Nanostructures, the state-of-the-art cleanroom of TU Wien.
"We only need a
few microliters of liquid for a measurement," says Borislav Hinkov.
"And the sensor delivers data in real time -- many times per second. Thus,
we can precisely monitor a change in concentration in real time and measure the
current stage of a chemical reaction in the beaker. This is in strong contrast
to other reference technologies, where you need to take a sample, analyze it
and wait up to minutes for the result."
Collaboration between
different disciplines is the key
This was made possible
by a collaboration between the departments of electrical engineering and
chemistry at TU Wien: the Institute of Solid State Electronics has extensive
experience in the design and fabrication of so called quantum cascade lasers
and detectors. They are tiny semiconductor-based devices that can emit or
detect infrared laser radiation with a precisely defined wavelength based on
their micro- and nanostructure.
The infrared radiation
emitted by such a laser penetrates the liquid on the micrometers-length scale
and is then measured by the detector on the same chip. Using these specially
combined ultra-compact lasers and detectors, a sensing device was realized, and
its performance was tested in first proof-of-concept measurements. The work was
conducted in collaboration with the group of Bernhard Lendl from the Institute
for Chemical Technologies and Analytics.
Experimental
demonstration: a protein changes its structure
To demonstrate the
performance of the novel mid-infrared sensor, a reaction from biochemistry was
selected: a known model protein was heated, thereby changing its geometrical
structure. Initially, the protein has the shape of a helix-like coil, but at
higher temperatures it unfolds into a flat structure. This geometrical change
also changes the particular mid-infrared fingerprint absorption spectrum of the
protein. "We selected two suitable wavelengths and fabricated suitable
quantum-cascade-based sensors, which we integrated onto a single chip,"
says Borislav Hinkov. "And indeed, it turns out: you can use this sensor
to observe the so-called denaturation of the selected model protein with high
sensitivity and in real time."
The technology is
extremely flexible. It is possible to adjust the necessary wavelengths as
needed in order to study different molecules. It is also possible to add
further quantum cascade sensors on the same chip to measure different
wavelengths and thus distinguish the concentration of different molecules
simultaneously. "This opens up a new field in analytical chemistry:
Real-time mid-infrared spectroscopy of liquids," says Borislav Hinkov. The
possible applications are extremely diverse -- they range from the observation
of thermally induced structural changes of proteins and similar structural changes
in other molecules, to the real-time analysis of chemical reactions, for
example in pharmaceutical drug production or in industrial manufacturing
processes. Wherever there is the need to monitor the dynamics of chemical
reactions in liquids, this new technique can bring important advantages.
The work was funded by
a Lise-Meitner grant from the FWF to Borislav Hinkov and by the EU Horizon2020
project "cFlow."
https://www.sciencedaily.com/releases/2022/08/220830093220.htm
No comments:
Post a Comment