KAIST

< Research team members, from left: student Jeong Yeon Han, Department of Chemistry, KAIST; Professor Jung-Moo Heo, Department of Applied Chemistry, Ajou University; Professor Kyung Jin Lee, Department of Chemical Engineering and Applied Chemistry, Chungnam National University; and Professor Dong Ki Yoon, Department of Chemistry, KAIST >

A new pathway has opened for controlling the rotation direction of light simply by changing how molecules are arranged, without having to synthesize complex new materials. Circularly polarized light is a special form of light that travels while rotating like a pinwheel either to the left or to the right. Because different rotation directions can carry different information, it is drawing attention as a key light source for next-generation displays, optical communications, and security technologies. KAIST researchers have developed a platform technology that arranges symmetric molecules into “microscopic pinwheels,” enabling circularly polarized light with a desired rotation direction.

< Figure 1. Fabrication of microscale pinwheel-shaped chiral structures from symmetric molecules, illustrated through a paper-folding analogy >

KAIST (President Choongsik Bae) announced on August 14 that a research team led by Professor Dong Ki Yoon from the Department of Chemistry, in collaboration with researchers from Chungnam National University, Ajou University, Yonsei University, and Japan’s RIKEN, has developed a technology that spatially confines symmetric non-chiral liquid crystal molecules and applies an electric field to form micrometer-scale chiral pinwheel structures, then permanently replicates them onto polymer nanofibers.

Chirality refers to the property of an object whose mirror image cannot be perfectly superimposed on the original, like a person’s left and right hands. Chirality is a key property not only of biological molecules such as proteins and DNA, but also of optical materials used in next-generation displays, optical sensors, and optical communications.

Until now, producing chiral optical materials has generally required the complex synthesis of molecules with asymmetric structures or the addition of large amounts of chiral substances. This has made fabrication complicated, limited the range of usable materials, and made it difficult to realize chiral structures with the same handedness over a large area.

To address this challenge, the research team proposed a new approach based on the idea that “structure creates function.”

< Figure 2. Formation of symmetry-broken chiral structures using microchannels and an electric field >

The team applied to molecules the same principle by which the same sheet of paper can form either a clockwise or counterclockwise pinwheel depending on how it is folded. They focused on the fact that even symmetric molecules can form structures with different handedness depending on how they assemble.

The researchers first induced rod-shaped molecules to self-assemble into microscopic pinwheel-like structures. They then added an extremely small amount of chiral additive, less than 1% of the total material, to guide all of the pinwheels to face the same direction. The team then successfully replicated this structure onto polymer nanofibers.

When a conventional luminescent material was coated onto this structure, circularly polarized light rotating in opposite directions was emitted depending not on the luminescent material itself, but on the direction of the pinwheel structure. Circularly polarized light is a special form of light that rotates to the left or right as it travels, and because each rotation direction can carry different information, it can be used in next-generation displays, optical communications, and anti-counterfeiting technologies.

< Figure 3. Structure-induced circularly polarized luminescence achieved by incorporating achiral emitters >

In other words, the study showed that the properties of light can be controlled simply by changing the structure on which a light-emitting material is placed, rather than by changing the light-emitting material itself. Put simply, just as the same LEGO blocks can form completely different shapes depending on how they are assembled, the same molecules can produce different optical properties depending only on how they are arranged.

Professor Dong Ki Yoon said, “The key point of this study is that we controlled the rotation direction of light not through the complex chemical structure of chiral molecules, but only through the way molecules are arranged,” adding, “This work presents a new optical material design principle that can be applied to next-generation displays, AR and VR optical devices, polarization sensors, and optical communications without the need to develop complex new materials.”

Jeong Yeon Han, the first author and a Ph.D. candidate, explained, “In conventional approaches, left-handed and right-handed structures tended to form together, canceling out chiral properties. In this study, however, we succeeded in aligning the structures in a single direction over a large area by designing an extremely small amount of additive to select only one rotation direction.”

This study was led by Ph.D. candidate Jeong Yeon Han as the first author, and the research results were published in the international journal Nature Communications on August 05.

Paper title: Microchiral pinwheel arrays based on achiral molecules,
DOI: 10.1038/s41467-026-76089-z
Authors: Jeong Yeon Han (first author), Won Kyung Park, Byeongil Noh, Fumito Araoka, Sungwook Jung, Byeong Hak Jhun, Youngmin You, Yoonsu Park, Kyung Jin Lee*, Jung-Moo Heo*, and Dong Ki Yoon* (*corresponding authors)

This research was supported by the Technology Innovation Program of the Ministry of Trade, Industry and Energy, the InnoCORE Program of the Ministry of Science and ICT, and the National Research Foundation of Korea.