Description du sujet de thèse

The ANR TRAINGEL project aims to extend the concept of training from glasses to gels, a relatively underexplored area so far. We hypothesize that colloidal and macromolecular gels will exhibit unique responses to training, potentially leading to novel structural and mechanical properties, such as increased strength, reduced elasticity, or induced anisotropy.

Description of the subject thesis:
1) Training highly concentrated anisotropic gels under frontal filtration and ultrasound:
Recently during the combined action of frontal filtration (FU) and ultrasound (US) on cellulose nanocrystal (CNC) aqueous suspensions, a typical three-layer orthotropic structure that resembles the articular cartilage organization was achieved in one step processing (Pignon et al. 2024, Bosson et al., 2025). Another interesting point evidenced is that starting from an initial concentration of 10 wt% the combined effect of FU and US have allowed to attain very high CNC concentration (59 wt %) near the membrane surface with cholesteric organization.
This novel well oriented highly concentrated phase, could not been achieved by simple mixing of dry CNCs in water. In this way, the training by combined FU/US processes on this kind of anisotropic liquid crystal-like colloidal gels will allowed to develop new concentrated materials with specific cholesteric organizations. It will be then very interesting to get insight in the relationships between the structural changes under flow of this specific highly concentrated cholesteric systems and its viscoelastic behavior in small deformation as well as out of equilibrium stresses evolutions under increasing steady shear flow. We will combine in-situ SAXS and SALS under shear flow as well as local birefringence combined with SALS to access to the changes in organizations from nanometer to micrometer length scales.

2) Application to Cell Culture and Tissue Engineering: development of orthotropic hydrogels based on CNCs by frontal filtration, ultrasound and UV-Curing or acidification.
The objective of this part is to develop three-dimensional hydrogels for cell culture or tissue engineering. Thanks to new processing methods combining the innovative ultrafiltration/ultrasound (UF/US) process and photocrosslinking or acidification at the end of the UF/US process, we will develop multilayer cellulosic-based hydrogels, composed of CNCs, PEGDA or alginate. The challenge will be to study in detail the resistance to shear, tensile and compressive forces by in situ SAXS, SALS, and ex situ SEM, XRD and tensile/compression tests. Cytocompatibility tests will be performed to evaluate the compatibility of the designed biomaterials. The optimization of the different processes (filtration, ultrasound, photopolymerization, acidification) and the evaluation of their cytocompatibility will open these new orthotropic cellulose composites to applications in tissue engineering as well as 3D cell culture. Furthermore, the effect of UF/US-induced CNC orientations on cell mobility, viability and directed proliferation will be studied under different ratio conditions (US/trans-membrane forces) as well as different types of UV-curable (PEGDA) or acidified (alginate) matrices.

Contexte de travail

The work will be carried out primarily at the Laboratoire Rhéologie et Porcédés (LRP) (http://www.laboratoire-rheologie-et-procedes.fr/) and will be supervised by Frédéric Pignon.
The work will be carried out primarily at the Rheology and Processes Laboratory (LRP) (http://www.laboratoire-rheologie-et-procedes.fr/) and will be supervised by Frédéric Pignon.
The Laboratoire Rhéologie et Porcédés (LRP) is a Joint Research Unit (UMR5520) combining the CNRS (Engineering Center, sections 10, 9, and 11), the University of Grenoble Alpes, Physics, Engineering, Materials (PEM) research center, and Grenoble, INP Institute of Engineering and Management, UGA.
The LRP, which is structured as a single team, consists of 30 permanent and 19 non-permanent staff members.
The research project currently involves a doctoral student and a postdoctoral fellow.

As part of the ANR TRAINGEL program, this project involves collaboration with three other laboratories and academic partners: the Physics Laboratory at ENS Lyon (in collaboration with Thomas Gibaud), the Molecular, Macromolecular, and Materials Chemistry Laboratory (C3M) at ESPCI in Paris (in collaboration with Stephano Aime), and the University of Vienna in Austria, in collaboration with Roberto Cerbino (Soft Matter eXperiments Lab) and Christos Likos (Faculty of Physics). Regular exchanges will be established with these laboratories, which will provide their respective expertise and support.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.

Contraintes et risques

There are no potential risks associated with the project, as long as current safety instructions in the laboratory are followed.

Informations complémentaires

References associated to the project:

Pignon F., Guilbert E., Mandin S., Hengl N., Karrouch M., Jean B., Putaux J.L., Gibaud T., Manneville S., Narayanan T., “Orthotropic organization of a cellulose nanocrystal suspension realized via the combined action of frontal ultrafiltration and ultrasound as revealed by in situ SAXS”, Journal of Colloid and Interface Science, 659, 914-925 (2024). https://doi.org/10.1016/j.jcis.2023.12.164.

Bosson F., Chèvremont W., Karrouch M., Blésès D., Delplace V., Hengl N. and Pignon F., “In situ multiscale characterization of cellulose nanocrystals orthotropic organization achieved by combining ultrasound and frontal ultrafiltration”, Carbohydrate Polymers, 362, 123680 (2025). https://doi.org/10.1016/j.carbpol.2025.123680

Bosson F., Challamel M., Karrouch M., Hengl N., Djeridi, H. and Pignon F., “Rayleigh streaming phenomena at the physical origin of cellulose nanocrystals orientations during combined ultrasound and ultrafiltration processes”, Nanoscale, 17, 14381-14393 (2025). https://doi-org.insis.bib.cnrs.fr/10.1039/D5NR00521C