Dr. Chang-Lyoul Lee's collaborative research team develops a fluorescent viscosity sensor that reveals microscopic viscosities of living cells 

□ Dr. Chang-Lyoul Lee of the Advanced Photonics Research Institute (APRI, Director Byeong Ha Lee) at the Gwangju Institute of Science and Technology (GIST, President Seung Hyeon Moon) has developed a fluorescent viscosity sensor that can measure the viscosity of a micro fluidic based on a unique molecule rotator * incorporating two rotating bodies.

* Organic molecules that can rotate because a specific part of an organic molecule is composed of a single bond is called a molecular rotating body.

∘ The change in the viscosity of a substance in a microscopic and macroscopic environment is a very important property of a substance in basic research and applications in the fields of medicine, life sciences, and materials. Changes in blood or intracellular viscosity are closely related to various diseases. For example, in the manufacturing process of plastics, the degree of polymerization of plastic and the variation of mechanical properties called glass transition temperature are very closely related to changes in the viscosity of the material.

∘ Therefore, a high-efficiency fluorescent viscosity sensor capable of confirming viscosity change in real time can be widely used in a wide variety of areas.

□ Fluorescent viscosity sensors for microfluidics have high fluorescence efficiency as well as high fluorescence contrast ratio according to viscosity change. However, in the conventional fluorescence viscosity sensor using a single rotating body, when a rotating body with a high degree of rotational freedom is introduced, the fluorescence contrast ratio is high but the fluorescence efficiency is low. On the other hand, when the fluorescence efficiency is high while the contrast ratio is low.

∘ Fluorescent viscosity and fluorescence contrast ratio, which are not optimized, have been obstacles to various application.

□ The researchers have succeeded in developing a fluorescence viscosity sensor molecules that have simultaneous high fluorescence efficiency and high fluorescence contrast ratio by introducing two sieves to overcome the drawback of fluorescence viscosity sensors using one existing rotating body. They have optimized the fluorescence efficiency and fluorescence contrast ratio by introducing a rotator that has a high electron donor * capability and high rotational degrees of freedom at the same time.

* It refers to atoms, ions, or molecules that easily give up electrons.

□ Dr. Chang-Lyoul Lee said, "Conventional fluorescence viscosity sensors using only one rotating body have a disadvantage in that the fluorescent contrast ratio is low when the fluorescence efficiency is high, and the fluorescence efficiency is low when the fluorescent contrast ratio is high. Optimization of the fluorescence efficiency and fluorescence contrast ratio of the molecular viscosity sensor using two rotating bodies was greatest significance of this research."

□ Professor O-Pil Kwon and Dr. Sehoon Kim said, "The molecular fluorescence viscosity sensor incorporating the two rotors in this study will enable the study of the viscosity of micro-microfluidics, which is difficult to measure with traditional physical methods. The design method of introducing two rotating bodies is expected to be applied not only to the fluorescence viscosity sensor but also to various molecular rotational studies."

□ This research was supported by the Research Support Project supported by the Korea Research Foundation, the Center for Leading Research, the Bio-Imaging Center Support Project supported by the Ministry of Health and Welfare, and the GIST Development Project. Their research was selected as a cover paper by Chemistry-A European Journal on December 5, 2017. In addition, this paper was selected for the Very Important Paper (VIP) paper to be awarded to top 5% level papers.