A metamaterial that increases the detection signal of infrared spectroscopy by 100 times has been developed, which is expected to improve the economic efficiency of the process of detecting hazardous substances and biomolecules.

Researchers at the Korea Institute of Machinery and Materials (President Park Sang-jin), under the Ministry of Science and ICT, and UNIST (President Lee Yong-hoon) announced on May 31st that they have developed a metamaterial that could dramatically improve the detection process of hazardous substances and biomolecules. The research results were published in the journal "Small Methods."

A joint research team led by Principal Researcher Jooyeon Jeong of the Nano Process Equipment Laboratory at the Korea Institute of Machinery and Materials and Professor Jongwon Lee of the Department of Electrical and Electronic Engineering at UNIST has developed a metamaterial that amplifies the infrared spectroscopy detection signal, which analyzes the components of a target by irradiating it with infrared light, by more than 100 times. Metamaterials are special functional materials with ultrafine structures arranged on their surfaces, each shorter than the wavelength of light.

Infrared spectroscopy detection is a technique that uses the characteristic of molecules of a substance to absorb infrared rays of a specific frequency to identify the components through the pattern of reflected light. At this time, if the substance to be detected is contained in only a very small amount, it is difficult to read because the difference in intensity of the light, which is the detection signal, is almost nonexistent.

In contrast, utilizing the newly developed metamaterial, the microscopic structures on its surface collect light energy and then direct it directly at the molecules, increasing the intensity of light absorbed by the molecules. This amplifies the detection signal, enabling clear results even with small amounts.

The metamaterial is constructed by sequentially stacking metal, insulator, and metal in a cross shape. The central insulator is thinned to 10 nanometers and cut horizontally to create a vertical gap, maximizing the exposure of molecules to the near field and enhancing their light absorption.

“The newly developed metamaterial achieved a record-breaking detection signal of 36% reflection difference in a single-molecule layer detection experiment with a thickness of 2.8 nanometers,” said Hwang In-yong, a researcher at UNIST’s Department of Electrical Engineering. “We experimentally demonstrated the highest record in a single-molecule layer detection experiment.”

In particular, the metamaterial developed this time is easy to mass-produce and the manufacturing process is economical. Previously, expensive, high-resolution beam lithography processes were required to create microstructures on the surface of metamaterials, but the newly developed metamaterial can be easily manufactured using only nanoimprinting and dry etching processes.

Jeong Ju-yeon, a senior researcher at the Korea Institute of Machinery and Materials, said, “Using the nanoimprinting method, we can thinly layer metal-insulator-metal in that order, and then process the metal and insulator into the desired shape.” She added, “By adding a dry etching process, we can mass-produce metamaterials arranged in microstructures.”

Professor Jong-Won Lee of UNIST said, “This is the first study to simultaneously solve the problem of near-field strength enhancement and near-field exposure through a vertical gap structure,” and added, “It is expected to be widely applied in sensor technology that detects biomolecules, hazardous substances, and gases using infrared.”

The results of this study were published on May 13th in Small Methods, a leading international nanoscience journal published by Wiley. The research was supported by the Ministry of Science and ICT's Global Frontier Wave Energy Extreme Control Research Group and the National Research Foundation of Korea's Nanomaterials Technology Development and Civilian-Military Dual-Use Technology Development Program.