Optical sorting of cholesteric liquid crystal droplets

Informations projet

OPS-CLC

N° de convention de subvention: 101067273

DOI

10.3030/101067273

Projet clôturé

Date de signature de la CE 22 Août 2022

Date de début 1 Septembre 2023

Date de fin 31 Août 2025

Financé au titre de

• Marie Skłodowska-Curie Actions (MSCA)

Coût total

Aucune donnée

Contribution de l’UE

€ 209 400,88

Coordonné par

UNIVERSITE DE BORDEAUX
France

Periodic Reporting for period 1 - OPS-CLC (Optical sorting of cholesteric liquid crystal droplets)

Période du rapport: 2023-09-01 au 2025-08-31

Résumé du contexte et des objectifs généraux du projet

The OPS-CLC project (Optical Sorting of Cholesteric Liquid Crystal Droplets) explored how light can distinguish and control microscopic chiral objects—structures that differ from their mirror image, like right and left hands. Chirality is a universal property in nature and technology, shaping the behaviour of molecules, biological systems, and advanced materials. Yet, separating or manipulating right- and left-handed species remains a challenge in chemistry, pharmacology, and materials science, where conventional methods depend on chemical agents or mechanical contact.
OPS-CLC proposed a radically different, contact-free optical approach. The project aimed to show that linearly polarised light, containing equal left- and right-handed circular components, could exert opposite torques on cholesteric liquid-crystal droplets of opposite handedness—creating a purely optical form of enantioseparation powered by light’s angular momentum rather than chemical or mechanical means.
Hosted at the University of Bordeaux’s Laboratoire Ondes et Matière d’Aquitaine (LOMA), an international centre of excellence in optics and soft-matter physics, the project combined expertise in optical engineering, fluid dynamics, and material science to develop a state-of-the-art optofluidic platform for studying chiral light–matter interactions.
Through this work, OPS-CLC addressed both fundamental and strategic needs: understanding how chirality governs light–matter interaction, and laying the groundwork for cleaner, energy-efficient technologies capable of manipulating microscopic systems without contact. By bridging advanced photonics and soft-matter science, the project contributed to Europe’s goals of sustainable innovation and technological leadership in advanced materials. Its impact spans from fundamental physics—deepening knowledge of chiral dynamics—to potential applications in microfluidic sorting, optical sensing, and enantioselective manufacturing, reinforcing Europe’s position at the forefront of next-generation light-driven technologies.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

During the OPS-CLC project, a fully functional optical–fluidic platform was developed at the Laboratoire Ondes et Matière d’Aquitaine (LOMA), University of Bordeaux, to study the interaction between light and chiral soft matter. The system combined a continuous-wave green laser, spatial-light-modulator control for precise wavefront shaping, a custom microfluidic chamber for droplet injection, and a high-resolution polarising microscope with interferometric diagnostics. After calibration with isotropic reference particles, the setup achieved the required optical stability and sensitivity, meeting the initial technical objectives.
Experiments on single cholesteric liquid-crystal droplets revealed an unexpected limitation: the internal disclination line defining droplet symmetry could not be stabilised along the optical axis. This instability, caused by strong hydrodynamic coupling with the surrounding fluid, masked the expected optical-torque signal. Although this prevented direct observation of the intended enantioseparation effect, it exposed a new physical problem—the coupling between topological defects and viscous flow in chiral droplets.
To address this, the project introduced a secondary control mechanism based on structured magnetic fields exploiting the weak diamagnetic anisotropy of the liquid-crystal material. This provided reliable orientation control in simplified geometries and enabled systematic studies of defect organisation and symmetry breaking in confined liquid-crystal layers. The approach led to a peer-reviewed publication in Soft Matter and a presentation at an international conference, both acknowledging MSCA support.
Building on these results, the research evolved toward planar cholesteric systems. The fellow and supervisor developed multilayer chiral mirrors made of two cholesteric films of opposite handedness separated by a transparent spacer. These structures act as photonic cavities that enhance optical activity and circular dichroism, providing a stable, scalable platform to amplify light–chirality coupling.
Through this work, OPS-CLC established a reusable experimental platform, identified key physical constraints on optical control of chiral droplets, and opened a new research line on chiral photonic cavities that extends the project’s goals while maintaining full scientific coherence.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

OPS-CLC advanced the frontier of light–matter interaction in chiral soft materials by experimentally identifying the physical limits governing optical torque in cholesteric liquid-crystal droplets. Although the anticipated demonstration of optical sorting could not be achieved due to dominant hydrodynamic effects, the project revealed that the interplay between viscous flow and topological defects critically shapes the mechanical response of chiral droplets under illumination. This finding adds a new dimension to the understanding of non-equilibrium behaviour in soft matter, extending the state of the art in singular optics and liquid-crystal physics.
The project also introduced a symmetry-guided magnetic control strategy to manipulate defect orientation in anisotropic fluids. This provided the first systematic framework for designing magnetic-field configurations that stabilise topological structures in liquid crystals, offering a path toward hybrid optical–magnetic control of chiral materials. The methodology was validated experimentally and published in Soft Matter (Royal Society of Chemistry, 2025), establishing a reproducible, open-access reference for the community.
Building on these insights, OPS-CLC initiated a new research line on planar chiral mirrors—multilayer photonic cavities made of two cholesteric films of opposite handedness separated by a transparent spacer. These structures enhance optical activity and circular dichroism, providing a stable, scalable platform to study and exploit chirality-dependent light propagation. The concept opens perspectives for tunable polarisation optics, biosensing, and compact photonic components based on chirality amplification.
The reusable optofluidic setup and open-source data and code repository ensure that the project’s results can be directly expanded by other researchers. Future work could couple the optical platform with magnetic or acoustic actuation to achieve full control of chiral dynamics, or adapt the planar-mirror geometry for integration into photonic devices. Potential intellectual-property outcomes will be assessed in collaboration with Aquitaine Science Transfert, the University of Bordeaux’s technology-transfer office.
Overall, OPS-CLC delivered new physical understanding, experimental tools, and material architectures that push chiral photonics beyond the current state of the art, laying the groundwork for both fundamental and applied advances in light-driven soft-matter technologies.

Conceptual illustration of the OPS-CLC project