Abstract
Chiral active Brownian particles convert stored or environmental energy into self-propulsion and rotation, driving systems far from equilibrium. How chirality influences diffusion in crowded environments composed of deformable and displaceable obstacles remains poorly understood. Here we show, through combined experiments and theory, that chiral active Brownian particles confined in an annular channel with deformable and displaceable ring obstacles exhibit a pronounced nonmonotonic dependence of diffusivity on obstacle density. The diffusion coefficient initially increases and then decreases with obstacle area fraction, reaching enhancements of nearly two orders of magnitude. Experiments and theory indicate that this behavior originates from a competition between obstacle-induced motion collimation and suppression of migration velocity. The enhancement also varies nonmonotonically with particle orbital radius due to differences in intrinsic free-space diffusivity. These findings provide insight into nonequilibrium transport in dynamically reconfigurable environments and suggest strategies for controlling chiral active matter in complex media.
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The data supporting the findings of this study are available in the main text and Supplementary information. Supplementary Movie 1 and Supplementary Movie 2 are uploaded as Supplemental Material, and the data used to obtain in the plots are available as the Supplementary Data. Additional information is available from the corresponding author upon request.
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Acknowledgements
We acknowledge the supports of the National Natural Science Foundation of China (Grants No. 12374205, No. 12304245, No. T2325027, No. 12274448, and No. 12475031), the Shandong Provincial Natural Science Foundation (Grant No. ZR2024YQ017), the Science Foundation of China University of Petroleum, Beijing (Grants No. 2462024BJRC010 and No. 2462023YJRC031), and the Beijing Institute of Technology Research Fund Program for Young Scholars. This work was also supported by Beijing National Laboratory for Condensed Matter Physics (Grants No. 2024BNLCMPKF009).
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N.Z., L.N., P.L., and M.Y. conceived the research. N.Z., L.N., and K.Z. conducted the experiments. K.Z., Y.T., H.Z., and X.Y developed the video analysis code. K.Z. and H.Z. performed data analysis. N.Z., L.N., P.L., M.Y., and Y.L. supervised the research. All authors discussed the results and contributed to writing the manuscript.
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Zhang, K., Tian, Y., Yu, X. et al. Unusual diffusion of chiral active Brownian particles in deformable and displaceable media. Commun Phys (2026). https://doi.org/10.1038/s42005-026-02591-x
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DOI: https://doi.org/10.1038/s42005-026-02591-x
