Korean researchers were the first in the world to develop technology for detecting minute amounts of transparent liquid with the naked eye.

SNU College of Engineering announced on the 12th that the research team of SNU ECE Professor Sin-Doo Lee, Ph.D. Yong-Sang Ryu of KIST (Korea Institute of Science and Technology), and student Eui-Sang Yu under joint supervision (first author, SNU-KIST dispatch) developed a technology to detect minute amounts of transparent liquids with the naked eye by using resonators with the thickness of tens of nanometers.

This research opens up possibilities for applications such as an environmental sensor for hazardous materials since it can detect liquid by color without capacious optical instruments or expensive measuring devices. Also, it can be used for the security of optical reserved information that is saved according to the refractive index of the liquid or gas entering the nanostructure.

The research team proposed a metal-insulator-metal (MIM) structure where hollow voids of nanometer-scale are formed within the dielectric layer so that liquid or gas can penetrate. They invented a method to manufacture this structure with a single reactive-ion etching(RIE) process. Furthermore, they adopted the concept of using the top metal layer that depends on the deposition speed also as an etching mask, and thus was able to easily manipulate the nanospace within the dielectric layer.

The liquid or gas infiltrating this novel MIM structure generates various colors by changing the resonant wavelength to its maximum within the visible light spectrum depending on its refractive index. Consequently, the returned color values can be differentiated with the naked eye. Such results are expected to have a significant impact on the development of sensors that are highly sensitive, low-priced, lightweight, and small in size.

KIST Ph.D. Yong-Sang Ryu commented, “Based on this research, we have developed methods to visualize the changes due to liquids, gases, humidity, and temperature. We will develop early detection and response sensors of hazards posing risks to citizen health and directly harmful material.”

On the 7th, the research results were published on the cover of the world-renowned journal ‘ACS Applied Materials and Interfaces’. This research was funded by KIST, the Ministry of Trade, Industry and Energy, and SNU BK21 Information Technology.

Source: http://ee.snu.ac.kr/community/news?bm=v&bbsidx=48111
Translated by: Jee Hyun Lee, English Editor of Department of Electrical and Computer Engineering, jlee621@snu.ac.kr