[Soft Matter Café] Typical three-layer orthotropic organization of articular cartilage achieved through the combined action of frontal ultrafiltration and ultrasound on cellulose nanocrystal suspensions, revealed by in situ SAXS.

Rodlike cellulose nanocrystals (CNCs) possess significant potential as building blocks for creating uniform, sustainable materials. However, a critical hurdle lies in the need to enhance existing or devise novel processing that provide improved control over the alignment and arrangement of CNCs across a wide spatial range. Specifically, the challenge is to achieve orthotropic organization in a single-step processing. In this aim, an original combined frontal ultrafiltration (FU) and ultrasound (US) set-up compatible with in situ SAXS observations has allowed revealing for the first time a multilayer orthotropic structuring of CNC suspensions, that mimics the organization of articular cartilage: a first layer composed of CNCs having their director aligned parallel to the horizontal membrane surface, a second intermediate isotropic layer, and a third layer of CNCs with their director vertically oriented along the direction of US wave propagation direction. These results open the way for developing novel orthotropic biomaterials with tunable structured cellulosic organizations for tissue engineering applications.

(Semeraro E. F. et al., Colloids Surf. A, 584,124030, 2020 doi.org/10.1016/j.colsurfa.2019.124030 ; Pignon F. et al., J. Phys. Chem. C, 125, 18409-18419, 2021 doi.org/10.1021/acs.jpcc.1c03506).

About the speaker:  Frédéric Pignon is Senior Scientist at CNRS in the “Laboratoire Rhéologie et Procédés” UMR 5520 (CNRS, Université Grenoble Alpes, Grenoble-INP). His main research interest is devoted to understand and control the multi-scale structure and flow properties of colloidal suspensions in industrial processes. For example, membrane separation processes combined with ultrasound are studied by in-situ scattering measurements (SAXS, SALS) in order to improve the performance of filtration as well as produce innovative cellulosic composite films with controlled anisotropic textures from nanometric to micrometric length scales.