By Amit Malewar Published: April 24, 2026
Collected at: https://www.techexplorist.com/light-particles-chirality/102781/
Chirality is a property of an object or molecule that describes whether something is “left‑handed” or “right‑handed” in shape. Chirality matters because in chemistry and biology, two mirror‑image forms of the same molecule can behave very differently.
Like right‑ and left‑handed screws twist differently, chiral particles respond differently when exposed to circularly polarised light.
In a new study, researchers from Tokyo University of Science (TUS), Japan; Institute for Molecular Science (IMS), Japan; and Seoul National University (SNU), Republic of Korea, have demonstrated that the evanescent field of optical nanofibres can selectively transport nanoparticles based on their chirality.
Light can push tiny objects by transferring momentum, creating a very small force. When the light is circularly polarised, this force depends on the particle’s handedness, pushing left‑ and right‑handed particles in different ways.
But as particles get smaller, their interaction with light weakens. At the same time, random motion becomes stronger, often overpowering the light’s ability to move them.
By sending circularly polarised light through these fibers, they discovered that left‑handed and right‑handed particles move at different speeds.
Even more impressively, when they sent light in opposite directions through the ultra-thin fiber, they could cancel out the non‑chiral forces. This meant particles moved purely according to their handedness, either forward or backward along the fiber.
Professor Mark Sadgrove’s group at TUS said, “While circularly polarized light has been used to separate microparticles (whose size is about the width of a human hair), applying the same approach to nanoparticles, which are 1,000 times smaller, has not been successful. Given that the eventual aim is to reach the size of a molecule (about 1–10 nm), this limitation is a serious problem.”
To solve the problem of weak forces on very small particles, researchers used tightly confined light. They did this with an ultra‑thin optical fiber, where light is concentrated near the fiber’s surface in a zone called the evanescent field. This setup creates a stronger, more focused push than ordinary light beams.
By sending circularly polarised light (light that twists like a corkscrew) through the fiber, they found that left‑handed and right‑handed particles felt different forces.
The team tested this using tiny metallic nanocubes with twisted faces, giving them a clear “handedness.” When placed near the fiber, the particles moved along it under the influence of the evanescent field. Their speed and direction depended on both their handedness and the light’s twist.
By switching the light’s twist between clockwise and anticlockwise, the researchers could reverse the particles’ response, changing the direction they moved. This allowed them to separate particles by chirality using light alone.
“When Dr. Georgiy Tkachenko showed me the first results, I was amazed,” says Prof. Sadgrove. “I never thought the effect would be strong enough to see so clearly in the data. It really shows the power of using ultra‑thin optical fibers for this kind of work.”
By demonstrating that light can selectively move chiral nanoparticles, the study offers a simpler, more effective way to control handedness at very small scales. Looking ahead, the researchers hope to extend this method to particles 10 to 100 times smaller, down to the size of individual molecules.
If successful, this could open new doors for studying chirality in biology and for designing better drugs, since the handedness of a molecule often determines how it interacts with the body.
Journal Reference:
- Tkachenko, G., Suda, A., Ahn, HY. et al. Chirality-selective optical transport of nanoparticles in the evanescent field of a nanofibre. Nat Commun 17, 3463 (2026). DOI: 10.1038/s41467-026-71585-8
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