Understanding the shear stress-driven cellular activities is crucial to develop innovative diagnoses, therapies, and medical devices. Because there exists no method to measure the rapidly varying shear stress (e.g. pulsatile blood flow) near cells, our knowledge of how flow regulates such a variety of cell functions is highly limited.
We develop a micro-tomographic shearmetry that allows 3D-mapping and monitoring of the time-dependent shear stress profile with unprecedented spatio-temporal resolution. This constitutes a breakthrough from the conventional approaches based on particle tracking methods within microfluidic chambers. We have developed a novel shearmetry technique through a radically different methodology based on capturing the shear-induced orientation behavior of luminescent nanorods [1, 2, 3]. These nanorods have been continuously optimized to be brightly luminescent, highly polarized, and stably dispersed in physiological media [4, 5, 6].  
In collaboration with A. Barakat group at LadhyX (Hydrodynamics lab at Ecole Polytechnique),

we investigate important mechanobiological questions in endothelial cells (ECs) lining the inner surfaces of blood vessels. The flow-induced intracellular calcium mobilization and the flow-induced endothelial wound healing will be examined. This project envisions to provide the new shearmetry platform as a universal experimental solution to measure, monitor, and analyze the dynamic shear stress distribution in a wide range of micro- and bio-fluidic systems and environments. 
 

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​[1] 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] 

[2] Z. Wang, Q. Zou, L. Magermans, G. Amselem, C. Dessalles, B. Louis, M. Filoche, T. Gacoin*, J. Kim* “Shearmetry of Fluids with Tunable Rheology by Polarized Luminescence of Rare Earth-Doped Nanorods” ACS Nano 18 30650 (2024). [Link]

[3] Q. Zou, Z. Wang, L. Magermans, M. Bonetti, T. Gacoin*, J. Kim* “Shearmetry in fluids by using size-controlled anisotropic LaPO4:Eu3+ nanorods as polarized luminescent probes” under review at Advanced Functional Materials

​[4] E Chaudan, J Kim*, S Tusseau-Nenez, P Goldner, O L Malta, J Peretti, T Gacoin* “Polarized luminescence of anisotropic LaPO4:Eu nanocrystal polymorphs” Journal of American Chemical Society. 140, 9512-9517 (2018). [Link]

[5] Z. Wang, F Delille, S Bartier, T Pons, N Lequeux, B Louis, J Kim*, T Gacoin* “Zwitterionic Polymers towards the Development of Orientation-Sensitive Bioprobes” Langmuir. 38, 34, 10512 (2022). [Link]

[6] Z. Wang, JM Kim, L. Magermans, F. Corbella, I. Florea, E. larquet, J. Kim*, T Gacoin* “Monazite LaPO4:Eu3+ nanorods as strongly polarized nano-emitters” Nanoscale. 13, 40, 16968 (2021). [Link]

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