Understanding Chirality and Handedness in Objects

Researchers from the Tokyo University of Science (TUS), the Institute for Molecular Science (IMS), and Seoul National University (SNU) have developed a method to selectively manipulate and sort metallic chiral nanoparticles using light. The study, published April 16, 2026, in Volume 17, Article number 3463 of the journal Nature Communications, demonstrates a way to control the movement of nanoscale objects based on their handedness.

Chirality, or handedness, is a geometric property where an object is not identical to its mirror image. This property is fundamental to biological systems; for example, the handedness of amino acids determines how they interact with other biological structures. While sorting chiral particles at the micrometer scale has been possible, achieving the same result at the nanometer scale has remained a challenge because the forces of light-matter interaction are often too weak to overcome random Brownian motion.

Harnessing the Evanescent Field

To overcome the limitations of conventional light beams, the research team utilized ultra-thin optical nanofibers. These fibers concentrate light near their surface in a region known as the evanescent field, which provides a highly localized and intensified electromagnetic environment.

The researchers used circularly polarized light, which twists like a corkscrew as it travels. By sending this light through the nanofiber, they created a situation where left-handed and right-handed nanoparticles experienced different forces. The experimental subjects were metallic nanocubes fabricated with precisely twisted faces to give them a defined chirality.

The team found that the speed and direction of the nanoparticles’ motion along the fiber depended on both the handedness of the particles and the polarization of the light. By switching the circular polarization between clockwise and anticlockwise, the researchers could reverse the response of the particles, effectively sorting them by their chirality.

“When Dr. Georgiy Tkachenko showed me the initial results, I was stunned. I never imagined that the effect would be large enough to show up in the raw data. I think this really shows the advantages of using such thin optical fibers for optical manipulation.”

Prof. Mark Sadgrove, Tokyo University of Science

Technical Collaboration and Execution

The project involved a multidisciplinary effort across three institutions. The original experiments were performed at TUS by first author Dr. Georgiy Tkachenko and second author Akiyoshi Suda, utilizing optical fiber techniques developed by Professor Mark Sadgrove’s group. The metallic chiral nanoparticles used in the study were developed by Professor Ki Tae Nam’s group at SNU and fabricated at IMS by Dr. Hyo-Yong Ahn.

Additional contributions to the research were provided by In Han Ha at SNU, as well as TUS students Yamato Iida, Ichiro Kurihara, and Koki Saito.

Implications for Drug Development

The ability to sort nanoparticles by chirality has significant implications for the pharmaceutical industry. In drug development, the handedness of a chiral molecule often determines its efficacy and safety, as different enantiomers can interact with biological systems in vastly different ways.

By providing a simpler and more effective way to control chirality at very small scales, this method offers a new tool for separating and designing drugs based on molecular handedness.

Looking forward, the researchers suggest that the approach could be scaled down further. If the technique can be extended to particles that are 10 to 100 times smaller than those used in this study, it may become possible to manipulate individual molecules. Such a development would enable new ways to study chirality within biological systems at the most fundamental level.