Tag Archives: #metamaterial

Metamaterial Improves Sensitivity of Infrared Absorption Spectroscopy 100 Times (Material Science)

KIMM and UNIST develop metamaterial that improves infrared spectroscopic detection signal 100 times; low-cost technique revolutionizes detection of harmful substances and biomolecules

A local research team, comprised of members of the Korea Institute of Machinery and Materials(KIMM) under the Ministry of Science and ICT and UNIST, developed a metamaterial absorber that significantly enhances the detection of harmful substances or biomolecules, and published their results in Small Methods.

The joint research team led by Principal Researcher Dr. Joo-Yun Jung of the Nano-Convergence Mechanical Systems Research Division at KIMM and Professor Jongwon Lee of UNIST developed a metamaterial that enhances infrared absorption spectroscopy through 100-fold amplification of detection signals. The proposed metamaterial is a special functional material with vertical nanogaps of a smaller size than infrared wavelength.

Infrared spectroscopy is a technique that identifies components based on patterns of reflected light by measuring the properties of molecules to absorb infrared of their intrinsic frequencies. If only small traces of the target substance are detected, the results will not be as significant due to the small difference in light intensity.

The proposed metamaterial gathers and releases light energy at once, thereby inducing a larger intensity of light that can be absorbed by molecules. The amplified signals allow more distinct results to be obtained even when working with small traces of substances.

Cross-shaped nanoantennas were formed in a metal-insulator-metal configuration. The middle insulating layer had a thickness of 10 nm; vertical gaps were employed to maximize light absorption by molecules.

(Left) The graphs show the measured reflection spectra of the metamaterial absorber developed by KIMM and UNIST. From top to bottom, the vertical nanogaps are 30, 15, and 10 nm. The black line represents the reflection spectra of the metamaterial absorber before ODT coating, and the red line shows the reflection spectra after ODT coating. The amount of sinking of the two lines is the amount of light gathered (= energy absorbed = lower reflection). The red line representing reflectance after ODT coating rises when the wavelength is between 3.4 and 3.5, indicating signal amplification. If no signals were detected, the graph should be the same as that of the blue line. The difference between the two values is approximately 36%.
(Right) Detected signal spectra of the metamaterial absorber developed by KIMM and UNIST. © The Korea Institute of Machinery and Materials (KIMM)

Inyong Hwang, a researcher of the Department of Electrical Engineering at UNIST, said, “The proposed metamaterial achieved a record-high difference of 36% in our demonstration on a monolayer with a thickness of 2.8 nm. This is the best record achieved to date among monolayer detection experiments.”

The proposed metamaterial can be easily mass-produced and offers low-cost manufacturing. While high-resolution beam lithography was required to form microstructures on metamaterial surfaces, the team’s SEIRA platform relies on more affordable nanoimprint lithography and dry-etching processes.

Dr. Joo-Yun Jung, principal researcher of KIMM, said, “Using the nanoimprint process, we can obtain metamaterials in the metal-insulator-metal configuration, and process them into desired patterns. On top of that, the dry etching process allows mass production of microstructured metamaterials.”

Professor Jongwon Lee of UNIST said, “Our study is the first to induce near-field enhancement and resolve near-field exposure using vertical gaps. The technique is expected to have vast applications, especially for infrared sensors used in the detection of biomolecules, harmful substances, and gases.”

The Korea Institute of Machinery and Materials(KIMM) is a non-profit government-funded research institute under the Ministry of Science and ICT. Since its foundation in 1976, KIMM is contributing to economic growth of the nation by performing R&D on key technologies in machinery and materials, conducting reliability test evaluation, and commercializing the developed products and technologies.

The research results were published in Small Methods, an international journal published by Wiley, on May 13, with the title “Ultrasensitive Molecule Detection Based on Infrared Metamaterial Absorber with Vertical Nanogap”. The study was conducted with the support of the Global Frontier Center for Advanced Meta-Materials under the Ministry of Science and ICT, and the Nano-Material Technology Development Program and Civilian-Military Technology Development Program of the National Research Foundation of Korea.

Featured image: (Left) SEM image of the metamaterial absorber developed by KIMM and UNIST. Top view shows cross-shaped antenna.
(Center) Side view of the microstructure of the metamaterial absorber developed by KIMM and UNIST.
(Right) Structure of the metamaterial absorber developed by KIMM and UNIST. Figure shows 10 nm vertical nanogaps. © The Korea Institute of Machinery and Materials (KIMM)

Provided by NST

Metamaterial Tiles Boost Sensitivity of Large Telescopes (Astronomy)

Low-cost, mass producible technology poised to help Simons Observatory yield new insights into how the universe began.

A multi-institutional group of researchers has developed new metamaterial tiles that will help improve the sensitivity of telescopes being built at the preeminent Simons Observatory in Chile. The tiles have been incorporated into receivers that will be deployed at the observatory by 2022.

The Simons Observatory is the center of an ambitious effort to measure the cosmic microwave background — electromagnetic radiation left over from an early stage of the universe — using some of the world’s largest and most sophisticated ground-based telescopes. These measurements will help improve our understanding of how the universe began, what it is made of and how it evolved into what it is today.

“The Simons Observatory telescopes will use a new ultra-sensitive millimeter-wave camera to measure the afterglow of the big bang with unprecedented sensitivity,” said lead author Zhilei Xu from the University of Pennsylvania. “We developed a new low-cost absorbing tile that will be used in the camera to absorb environmental emissions that can obscure the signals we want to measure.”

In the Optical Society (OSA) journal Applied Optics, the researchers show that the metamaterial microwave tiles they developed absorb more than 99 percent of millimeter wave radiation and retain their absorptive properties at the extremely low temperatures in which the millimeter-wave camera operates.

“Because the tiles can be made by injection molding commercially available materials, they are an economic, mass-producible and easy-to-install solution to what has been a long-standing problem,” said Xu. “With this technology, the Simons Observatory will transform our understanding of the universe from many aspects, including the beginning of the universe, the formation and evolution of the galaxies and the ignition of the first stars.”

Working at low temperatures

Ground-based millimeter-wave telescopes use receivers that are cooled to cryogenic temperatures to reduce noise and thus boost sensitivity. Receiver technology has advanced to the point where any amount of stray light can degrade the image while also decreasing the sensitivity of the detector. A better way to suppress stray light within the receivers would further increase their sensitivity to the very faint signals coming from deep within space.  

Caption: Thermal testing of the new metamaterial tiles in an advanced cryogenic facility showed that they could be effectively cooled to the cryogenic temperatures necessary.  Credit: Eric Sucar, Penn Today

However, developing a material that can suppress stray light while operating at such extremely low temperatures is quite challenging. Previous attempts resulted in materials that either couldn’t be cooled effectively to cryogenic temperatures or didn’t achieve the necessary combination of low reflectance and high absorption. Other solutions have also tended to be difficult to install or challenging to mass produce.

To overcome these challenges, the researchers turned to metamaterials because they can be engineered to achieve specific properties that don’t occur in nature. After complex electromagnetic simulation studies, the researchers designed metamaterials based on a material that combined carbon particles and plastic.

Reducing reflection

Although the plastic composite exhibited high absorption in the desired microwave region of the electromagnetic spectrum, the surface reflected a significant amount of radiation before it could get inside the material to be absorbed. To reduce the reflection, the researchers added an anti-reflective coating that was tailored using injection molding.

“The low-reflectance surface combined with high-absorption bulk material allowed the metamaterial absorber tiles to deliver excellent suppression of unwanted signals at cryogenic temperatures close to absolute zero,” said Xu.

Caption: Zhilei Xu installs 240 of the new absorptive tiles into an optics tube that will be used in the Simons Observatory Large Aperture Telescope Receiver. Credit: Zhilei Xu, University of Pennsylvania

After ensuring that tiles made of the new metamaterial could mechanically survive thermal cycles from room temperatures to cryogenic temperatures, the researchers verified that they could be effectively cooled to -272° C (-458° F) and then measured their optical performance. “We developed a custom test facility to measure the performance of the tiles with high fidelity,” said Grace Chesmore, a graduate student at the University of Chicago who led the optical measurements of this research. The testing showed that the metamaterial exhibited excellent reflectance properties with low scattering and that it absorbed almost all of the incoming photons.

“As detector sensitivity continues to improve for millimeter-wave telescopes, it becomes crucial to control scattered photons,” said Xu. “The successful combination of a metamaterial and injection molding manufacturing opens up many possibilities for millimeter-wave instrument scientific instrument design.”

The work was a result of a large global collaboration that included researchers from the University of Pennsylvania, the University of Chicago, Goddard Space Flight Center, Massachusetts Institute of Technology and other institutions.

Featured image: Caption: Researchers developed new metamaterial tiles that will improve the sensitivity of telescopes at the Simons Observatory by absorbing stray light. The top left photo shows one tile, with its anti-reflective surface shown in the insert. The bottom left photos show the back of the tile, and the right photo shows the assembly of 240 tiles installed on the wall of an optics tube. Credit: Zhilei Xu, University of Pennsylvania

Reference: Z. Xu, G. E. Chesmore, S. Adachi, A. M. Ali, A. Bazarko, G. Coppi, M. Devlin, T. Devlin, S. R. Dicker, P. A. Gallardo, J. E. Golec, J. E. Gudmundsson, K. Harrington, M. Hattori, A. Kofman, K. Kiuchi, A. Kusaka, M. Limon, F. Matsuda, J. McMahon, F. Nati, M. D. Niemack, A. Suzuki, G. P. Teply, R. J. Thornton, E. J. Wollack, M. Zannoni, N. Zhu, “The Simons Observatory: Metamaterial Microwave Absorber (MMA) and its Cryogenic Applications,” Applied Optics, 60, 4, 864-874 (2021). https://www.osapublishing.org/ao/abstract.cfm?uri=ao-60-4-864
DOI: https://doi.org/10.1364/AO.411711

Provided by The Optical Society

About The Optical Society

Founded in 1916, The Optical Society (OSA) is the leading professional organization for scientists, engineers, students and business leaders who fuel discoveries, shape real-life applications and accelerate achievements in the science of light. Through world-renowned publications, meetings and membership initiatives, OSA provides quality research, inspired interactions and dedicated resources for its extensive global network of optics and photonics experts. For more information, visit osa.org