The Breakthrough at Tokyo University of Science
In a remarkable advancement for nanotechnology, researchers at Tokyo University of Science (TUS) have demonstrated a novel method to sort twisted nanoparticles using light. This technique leverages the evanescent field around ultra-thin optical nanofibers to selectively transport chiral nanoparticles based on their handedness—left or right. Chiral nanoparticles, which are mirror images of each other but not superimposable, play a crucial role in fields like pharmaceuticals, where one enantiomer can be therapeutic while the other is ineffective or harmful. The study, published in Nature Communications on April 24, 2026, marks the first successful optical sorting of such particles at the nanoscale, opening doors to precise manipulation for drug development and advanced materials.
The research team combined expertise in optical fiber technology from TUS with chiral nanoparticle synthesis from Seoul National University and optical property analysis from the Institute for Molecular Science. By guiding circularly polarized light through nanofibers just 400 nanometers thick, they created forces that propel left-handed and right-handed gold nanocubes in opposite directions along the fiber. Switching the light's polarization reverses the motion, enabling efficient separation even for ensembles with size variations.
Understanding Chiral Nanoparticles and Their Importance
Chirality, or handedness, refers to the property of an object that is non-superimposable on its mirror image, like left and right hands. At the nanoscale, chiral nanoparticles exhibit unique optical, chemical, and biological properties due to their three-dimensional twist. In pharmaceuticals, chirality is critical: thalidomide's tragedy in the 1960s highlighted how one enantiomer causes birth defects while the other relieves nausea. Sorting pure enantiomers is challenging for molecules (1-10 nm), but this breakthrough scales it to nanoparticles (100 nm), a stepping stone to molecular-level control.
In Japan, where precision manufacturing drives industries like electronics and biotech, chiral materials promise next-generation sensors, catalysts, and displays. TUS's method addresses limitations of prior techniques like optical tweezers, which struggle with nanoparticles due to Brownian motion overpowering light forces. The evanescent field—light leaking from the nanofiber—provides strong, localized gradients ideal for nanoscale sorting.
Step-by-Step: How the Optical Sorting Technique Works
The process begins with fabricating chiral gold nanocubes, featuring twisted faces that confer handedness. These particles, about 100 nm, are dispersed in water and brought near a nanofiber.
- Step 1: Light Guidance. Circularly polarized laser light (right or left-handed) is launched into a tapered optical nanofiber, creating an evanescent field extending ~200 nm from the surface.
- Step 2: Chirality-Dependent Force. The field's spin-angular momentum interacts differently with left- and right-handed particles, generating longitudinal forces. Simulations predict a dissymmetry factor g_z ≈ -0.5, matching experiments where velocities differ by factors of 2.
- Step 3: Selective Transport. Particles aggregate along the fiber; handed ones move faster/directionally. Counter-propagating beams cancel non-chiral forces, isolating chirality effects.
- Step 4: Polarization Switch. Flipping polarization reverses direction, separating enantiomers in a tapered fiber setup.
- Step 5: Detection and Collection. Real-time imaging tracks motion; sorted particles collect at fiber ends for analysis.
Experiments showed velocities up to 609 μm/s for right-circularly polarized light on right-handed particles, versus 297 μm/s for left-handed ones, robust against size/form variations near peak circular dichroism wavelengths (~640 nm).
Key Researchers Driving the Innovation at TUS
Leading the effort is Professor Mark Sadgrove from TUS's Department of Physics, whose lab specializes in nano-optics and light-matter interactions using nanofibers. Sadgrove, with a PhD from the University of Auckland and over 45 publications, expressed astonishment at the results: "When Dr. Georgiy Tkachenko showed me the initial data, I was stunned. I never imagined the effect would be large enough to show up raw." First author Dr. Georgiy Tkachenko, a postdoc in Sadgrove's group, optimized the fiber setup.
Chiral nanoparticles were crafted by Dr. Hyo-Yong Ahn and Professor Ki Tae Nam from Seoul National University, while Professor Hiromi Okamoto from IMS provided insights into chiral optics. TUS students Yamato Iida, Ichiro Kurihara, and Koki Saito contributed to experiments, highlighting the university's student involvement in cutting-edge research.
Sadgrove's group at TUS focuses on trapping/manipulating atoms, nanoparticles, and photons with nanofibers, building on 20+ years of expertise. This interdisciplinary collaboration exemplifies Japan's strength in international nanoscience partnerships.
Tokyo University of Science: Pioneering Nanoscience in Japan
Founded in 1881, Tokyo University of Science is Japan's oldest and largest private science university, with over 20,000 students across four campuses. Ranked among Japan's top 20 institutions (EduRank 2026: 17th nationally), TUS excels in physics and nanotechnology, producing Asia's only private university Nobel laureate in natural sciences.
The Department of Physics emphasizes multidisciplinary research from theoretical astrophysics to experimental biophysics. Sadgrove's lab exemplifies this, pioneering nanofiber-based optical manipulation since his 2020 arrival. TUS invests heavily in facilities like cleanrooms and advanced optics labs, supported by MEXT grants and JSPS fellowships.
In 2026, TUS ranks #156 globally for nanotechnology (EduRank), behind UTokyo (#1 Japan) but leading private unis. This breakthrough underscores TUS's rise, with Sadgrove's h-index reflecting impactful work in quantum optics and nano-transport.
Japan's Nanotechnology Landscape and University Roles
Japan leads globally in nanotechnology, with ¥10 trillion (~$67B) government investment via MEXT's 2023 plan to boost top universities. UTokyo, Kyoto U, and Tohoku U dominate, but private institutions like TUS contribute uniquely through agile, applied research.
Nanotech R&D funding reached ¥200B in FY2025, focusing on chiral materials for pharma (e.g., enantiopure drugs market $100B+ globally). TUS benefits from JSPS programs like Postdoctoral Fellowships (deadline April 2026), fostering international talent.
Compared to national unis, TUS's private status enables faster collaborations, as seen with SNU and IMS. Japan's nano output: 10% global papers, top in patents per capita. Challenges include aging faculty (average 55+), addressed by MEXT's PhD recruitment drives.
Real-World Applications and Broader Impacts
This sorting method promises revolutionizing chiral drug production, reducing costs from chromatography (expensive for scale-up). Envision separating biomolecules for targeted therapies, asymmetric catalysis for materials, or sensors detecting chiral pollutants.
In Japan, where pharma giants like Takeda invest ¥1T annually in R&D, TUS's tech could integrate into manufacturing. Optically sorted nanoparticles enable polarized light devices for displays/quantum computing. Environmentally, chiral-selective remediation for pesticides.
Stakeholders: pharma firms praise scalability; academics note extension to molecules. Economic impact: Japan's nano market ¥5T by 2030, TUS breakthrough accelerates growth.
Read the full paper in Nature Communications
Challenges Overcome and Future Outlook
Prior challenges: weak chiral forces vs. Brownian motion for nanoparticles. TUS overcame via nanofiber confinement (high gradients), achieving 2x velocity difference. Future: scale to 10 nm molecules, integrate microfluidics for high-throughput.
Sadgrove envisions waveguide chips for lab-on-a-chip enantiomer separators. Japan's Moonshot R&D Program funds such innovations (¥100B+). TUS plans extensions to biological chiral objects like proteins.
Risks: nanofiber fragility, polarization stability. Solutions: robust coatings, feedback loops. Timeline: prototypes 2-3 years, commercial 5+.
Photo by Monineath Horn on Unsplash
Career Opportunities in Japan's Nanoscience Field
TUS breakthrough highlights booming careers in nano-optics. PhD/postdocs via MEXT scholarships (2027 apps open). Faculty positions at TUS/UTokyo emphasize interdisciplinary skills.
Industry: Fujifilm, Nikon hire for chiral tech. Salaries: postdoc ¥5-7M/year, professor ¥10M+. Programs like JSPS International Fellowships attract global talent. TUS offers research assistantships, aligning with Japan's 10T yen uni boost.
Conclusion: TUS Leading Japan's Nano Revolution
Tokyo University of Science's chiral nanoparticle sorting breakthrough exemplifies private unis' vital role in Japan's research ecosystem. By merging optics and nano-fabrication, TUS advances global science while training future leaders. As Japan invests heavily in nano, expect more innovations driving pharma, materials, and beyond.