Liquid crystals (LCs) represent topological active matter where transformable defects play a central role in their tunable physical properties. While various LC phases and topological structures have been identified in both natural and synthetic materials, their dynamics (i.e., time-dependent processes of morphogenesis and phase transition) remain largely unexplored. Moreover, complex three-dimensional (3D) topological and topographical structures have been overlooked due to the lack of observation methods other than traditional birefringence analysis. 
We have discovered a stepwise morphogenesis behavior of nematic colloids, which evolve from typical tactoids into strikingly novel topological and topographical structures under confinement. Using a cutting-edge orientational tomography method, we perform volumetric mapping of LC directors (topology) and domain interfaces (topography). This enables us to clearly demonstrate the complete morphogenesis process, which finally provides compelling insights into previously unexplored LC dynamics. In collaboration with T. Atherton group (Tufts University), we perform computer modelling that further reveals the delicate balance between volume and surface energies governing the observed structure and morphogenesis. Our discovery of the flower-shaped singularity structure coincides remarkably with the theoretical prediction made a half-century ago by Nobel Laureate Pierre-Gilles de Gennes. 
This project addresses a ground-breaking perspective on the dynamic behaviour of topological active matters, with broad implications across various sectors of physics including magnetism, spin dynamics, colloidal self-assembly, soft matter, and interfacial engineering. Furthermore, it establishes an unparalleled 3D characterization method based on polarized photoluminescence spectroscopy of lanthanides, applicable to various molecular and nanomaterials. 
 

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Related publications: ​​​​

​[1] L. Magermans, J-M. Kim, R. Chacon, A. Leray, T. Atherton, T. Gacoin, J. Kim* “Morphogenesis and Topological Evolution of Nematic Colloids under Confinement” under review

[2] J Kim*, S Michelin, M Hilbers, L Martinelli, E Chaudan, G Amselem, E Fradet, J-P Boilot, A M Brouwer, C N Baroud, J Peretti, T Gacoin* “Monitoring the orientation of rare-earth doped nanorods for flow shear tomography” Nature Nanotechnology. 12, 914-919 (2017). [Link]

[3] J-M. Kim, Z. Wang, K. Lahlil, P. Davidson*, T. Gacoin*, J. Kim* “Charge-driven liquid-crystalline behavior of ligand-functionalized nanorods in apolar solvent” The European Physical Journal E 46 (9), 86 (2023). [Link]

[4] J.-M. Kim, R. Chacón, Z. Wang, E. Larquet, K. Lahlil, A. Leray, G. Colas des Francs, J. Kim*, T. Gacoin “Measuring 3D Orientation of Nanocrystals via Polarized Luminescence of Rare-Earth Dopants” Nature Communications. 12, 1943 (2021). [Link]

[5] J.-M. Kim, K. Lahlil, T. Gacoin*, J. Kim*, “Measuring the order parameter of vertically aligned nanorod assemblies” Nanoscale. 13, 16, 7630 (2021). [Link]

[6] J Kim, J Peretti, K Lahlil, J-P Boilot, T Gacoin*, “Optically anisotropic thin films by shear-oriented assembly of colloidal nanorods” Adv. Mater. 25, 3295-3300 (2013). [Link]

[7] J Kim, A de la Cotte, R Deloncle, S Archambeau, C Biver, J-P Cano, K Lahlil, J-P Boilot, E Grelet, T Gacoin*, “LaPO4 mineral liquid crystalline suspensions with outstanding colloidal stability for electro-optical applications” Adv. Funct. Mater. 22, 4949–4956 (2012). [Link]       

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