Real-time ultrafast humidity sensing optical sensor

Date:
April 13, 2022
Source:
Pohang University of Science & Technology (POSTECH)
Summary:
A research team develops a real-time humidity sensing optical
sensor. The response time of the new sensor is 10,000 times faster
than the conventional sensors and can be mass-produced at low cost.



FULL STORY ==========================================================================
The Hercules beetle native to South America has a fascinating trait
of changing its shell colors depending on the external humidity
conditions. This is because the inside of the beetle's shell consists
of porous lattice structure with square holes. When light of particular wavelengths hits the shell, it reflects them and displays different
colors; and these wavelengths change depending on the humidity. Recently,
a sensor that changes colors depending on the humidity like this beetle
with 10,000 times faster speed than the conventional optical sensors
has been proposed.


==========================================================================
A POSTECH research team led by Professor Junsuk Rho (Department of
Chemical Engineering and Department of Mechanical Engineering) and
Ph.D. candidates Chunghwan Jung and Jaehyuck Jang (Department of Chemical Engineering), in collaboration with Sung-Hoon Hong and Dr. Soo-Jung
Kim (Electronics and Telecommunications Research Institute, ETRI) and
Professor Young Min Song (Gwangju Institute of Science and Technology,
GIST), has developed an ultrafast humidity-responsive colorimetric
sensor. The findings from the study were published in the top academic
journal Science Advances.

Sensors using light are already being used in our daily lives, for electrocardiogram and air quality measurement. These sensors use light
to detect changes in their surroundings and convert them into digital
signals.

The research team fabricated a colorimetric sensor that consists of metal- hydrogel-metal structure using a disordered metal nanoparticle layer --
a chitosan hydrogel -- and a reflecting substrate. When the external
humidity changes, the resonant frequency of the sensor changes due to
the characteristic of the chitosan hydrogel that swells under wet state
and contracts under dry state repeatedly.

This new sensor boasts an ultrafast speed that is 10,000 times
faster than the conventional Fabry-Perot interferometer based optical
sensors. This fast reaction speed is thanks to the porous space between
the nanoparticles that make up the sensor, much like the shell of the
beetle that changes colors depending on the humidity.

"This new humidity sensor is special in that it allows scalability of production at low cost even though nanomaterials and nanostructures
were used," explained Professor Rho who led the study. "Introducing the humidity-responsive color pixels into security codes enables application
toward security tags for humidity-sensitive electronic devices, banknotes, passports, and ID cards.

This study was conducted with the support from the Samsung Research
Funding & Incubation Center for Future Technology.


========================================================================== Story Source: Materials provided by Pohang_University_of_Science_&_Technology_(POSTECH).

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Chunghwan Jung, Soo-Jung Kim, Jaehyuck Jang, Joo Hwan Ko, Doa Kim,
Byoungsu Ko, Young Min Song, Sung-Hoon Hong, Junsuk Rho. Disordered-
nanoparticle-based etalon for ultrafast humidity-responsive
colorimetric sensors and anti-counterfeiting displays. Science
Advances, 2022; 8 (10) DOI: 10.1126/sciadv.abm8598 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220413104143.htm

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