Postdoctoral Position at ESPCI Paris

Dear colleagues,

I have an opening for an ANR funded post-doctoral position « Molecular Tribology : Watching individual liquid molecules moving at interfaces ». Details on the project can be found here: https://blog.espci.fr/jcomtet/files/2024/06/PostDocProposal_MoleculeTribology.pdf
 
Our lab is located at ESPCI PSL, Paris, France. Note that we recently moved to a brand new building with state-of-the-art research facilities.
 
Do not hesitate to forward this offer to potential candidates and contact me for more details if interested (jean.comtet@espci.fr).
 
Kind regards,
Jean Comtet
Associate CNRS Researcher
Laboratory for Soft Matter and Engineering
ESPCI, CNRS, Sorbonne University
Paris, France

proposition de thèse STLO-Rennes

MULTIDISCIPLINARY PH.D POSITION BETWEEN STLO (RENNES), FAST (ORSAY) AND LGC (TOULOUSE)

Multi-scale exploration of the drying dynamics of dairy colloids and their rehydration

Keywords : colloids, liquid-solid transition, evaporation kinetics, drying, dairy proteins APPLICATION BEFORE JUNE 28TH

Starting date : September-December 2024

Research description

Drying is a key stage in dairy processing, with 50% of collected milk dry matter currently being converted into powder. Due to the still relatively empirical control of the drying process, problems are encountered on an industrial scale, both in terms of product properties (non-conformity with expected properties, e.g. rehydration) and process performance (e.g. sticking). Indeed, the mechanisms of particle formation during spray drying are not yet fully understood, the drying chamber being a “black box” making on-line observation of droplet-particle formation impossible.

We therefore aim to develop a multi-scale physics approach that brings together two complementary approaches in a single, original scientific approach :

– a local approach, with detailed analysis of elementary phenomena based on fundamental laws and principles ;
– a systemic approach, integrating phenomena on a process scale, right down to rehydration properties in our case.

This exploration of drying dynamics represents a relevant method for observing the drying phenomenon directly, flexibly and in detail, and for understanding the influence of different colloids on the characteristics of the products obtained. Thus, the study of drying in a confined environment represents an interesting means of gathering new information on the behavior of matter in a concentrated state, consistent with what can be observed at higher scales.

The research questions addressed in this Ph.D. project will follow a deductive logic, from the observation of the phenomenon to its physical interpretation :

1. Direct observation of the organisation of dairy colloids during drying under controlled conditions.

What is the specific role of constituents preferentially involved in self-stratification mechanisms during evaporation of dairy colloidal dispersions ?

2. Physical interpretation of the various stages of the drying dynamics using model colloids. What are the mechanical and rheological parameters that govern the solid-liquid transition in dispersed colloidal systems ?

3. Transfer of knowledge acquired in 1D to 3D systems of binary colloid mixtures. What is the impact of stratification on the formation of interfacial skin during the drying of drops of colloid mixtures (dairy and model) ? How can we link the morphological characteristics of powder particles and their reconstitution in water, by characterizing water diffusion on the surface of the particles ?

Context

The Ph.D. work wil benefit from the fruitfull collaboration between the research teams of STLO (Rennes; https://eng-stlo.rennes.hub.inrae.fr/umr-stlo), the FAST (Orsay; http://www.fast.u-psud.fr/) and the LGC (Toulouse ; https://lgc.cnrs.fr/). This scientific synergy has been largely set off in the course of the last years and especially in the framework of the scientific network of the GDR SLAMM (Solliciter LA Matière Molle).

Candidate profile

The project is at the interface between several disciplines (physics, process engineering, dairy physicochemistry). A profile with a master’s degree in physics, with research experience in biological systems if possible, or in chemical or process engineering, will be preferable.

The potential candidate should have an interest for the investigation of soft matter physics and in particular colloidal systems, as well as an ability to work in a multidisciplinary team, combining fundamental research and potential functional applications in the industrial domain.

more informations: PhD project DRYMAP EN

Offre Postdoc (18 months) in Bordeaux – Starting date July 2024

Postdoc (18 months) in Bordeaux  – Starting date July 2024- extended deadline 1st June

Project: Light-actuation of Soft compartments by artificials nanomotors

In this Postdoc project, the candidate will experimentally investigate the dynamics and mechanics of soft compartments driven by light-actuated nanomotors.

Profile:  The candidate should have a PhD in physics, soft matter,  with strong expertise in experimental physics.


contact :
ulysse.delabre@u-bordeaux.fr and antoine.aubret@u-bordeaux.fr

Offre de thèse – simulation – Montpellier

Modeling the flow of fibers interacting with grains

Mixtures of fibers and grains are present in many materials. Raw earth constructions often include a significant proportion of fibers or straw. In the materials and pharmaceutical industries, nanocellulose fibers are used as additives to powders. In civil engineering, synthetic fibers, or geotextiles, are used to stabilize embankments and banks. Lastly, when recycling materials that include fibers (wood, glass or carbon fibers), a grinding step is generally performed before separating the fibers and granular constituents. Figure : Example of simulation of fibers confined in a grain bed (discrete element method). In these different examples, fibers make a major contribution to the mechanical strength of materials, notably via their intrinsic properties (length, stiffness, breaking point), their collective behavior through entanglement effects or the formation of cohesive aggregates. In this thesis, numerical simulations by discrete element method (DEM) will be used to investigate mixtures of fibers and grains. The packing and rheology of these systems will be studied, and the effects of the proportion of fibers and grains, fiber stiffness, friction, confining pressure and shear rate will be investigated. The structural and dynamical properties of the simulated systems will be computed in order to understand the collective mechanisms of segregation and entanglement between deformable fibers. The simulation results will complement and be compared with experimental data obtained in the context of a partnership with experimental groups in the Paris area. The candidate will be part of the PhyProDiv group which has a strong expertise in the numerical modeling of granular media and soft matter and collaborates on these topics with other Physics (L2C) and Mechanics (LMGC) groups in Montpellier. We seek a candidate with a strong background in physics, mechanics or applied mathematics. Experience and interest in numerical modelling and simulation will be highly appreciated. Ability to work in a team and good communication skills are important as the PhD student will work in close contact within a project involving several research groups (in Sorbonne Université Paris, CNRS and Saint Gobain). The PhD is fully funded through an ANR grant (ConFig ANR-23-CE30-0032), and will take place at UMR IATE in Montpellier, south of France. For more details on the project, motivated and qualified candidates are encouraged to apply using the contacts mentioned below and to send a CV and motivation letter.

References

– Vo, T. T., Nezamabadi, S., Mutabaruka, P., Delenne, J. Y., & Radjai, F. (2020). Additive rheology of complex granular flows. Nature communications, 11(1), 1476.

– Fakih, M., Delenne, J. Y., Radjai, F., & Fourcaud, T. (2019). Root growth and force chains in a granular soil. Physical Review E, 99(4), 042903.

– Rakotonirina, A. D., Delenne, J. Y., Radjai, F., & Wachs, A. (2019). Grains3D, a flexible DEM approach for particles of arbitrary convex shape—Part III: extension to non-convex particles modelled as glued convex particles. Computational Particle Mechanics, 6, 55-84.

Contacts : Jean-Yves Delenne, jean-yves.delenne@inrae.fr Virginie Hugouvieux, virginie.hugouvieux@inrae.fr

Offre Postdoc (18 months) in Bordeaux – Starting date July 2024

Postdoc (18 months) in Bordeaux  – Starting date July 2024

Project: Light-actuation of Soft comportments by artificials nanomotors

In this Postdoc project, the candidate will experimentally investigate  the dynamics and mechanics of soft compartments driven by light-actuated nanomotors.

Profile:  The candidate should have a PhD in physics, soft matter,  with strong expertise in experimental physics.


contact :
ulysse.delabre@u-bordeaux.fr and antoine.aubret@u-bordeaux.fr

 

PhD position on « Brittle-to-Ductile Yielding Transition in Colloidal Gels and Glasses »

PhD Project: Brittle-to-Ductile Yielding Transition in Colloidal Gels and Glasses

see link: 2024PhD_advertisement_BTD

Understanding the response of soft materials under stress is of paramount importance, both fundamentally and in applications. Very often, the mechanical response of the material is dictated by its interactions with surfaces. To overcome this issue and probe the intrinsic properties of materials, we will produce unique spherical beads of gel and glasses of millimetric size. The gels and glasses are based on colloidal particles. The gels consist in a homogeneous porous stress-bearing network structure and the glasses consist in a dense packing of the particles. Our objective is to rationalize the fate of the beads under a mechanical compression, and especially understand how they yield. We want to investigate the complex interplay between the flow of liquid through the pores (the poroelasticity), the plasticity and fracture of the structure. We expect to unveil the physical mechanisms that control whether a bead of gel or glass yields in a brittle or ductile manner.

We will use a multiscale approach that combines mechanical measurements under compression, image analysis, and time- and space-resolved light scattering. We will explore several strategies to produce unique beads of colloidal gels and glasses with tunable toughness and brittleness. We will build an optical set-up to measure with a space and time resolution the microscopic rearrangements of the colloids in the bead during compression. We will measure concomitantly the mechanical response of the bead to the compressive stress and image the overall behavior of the bead.

The work will be performed within the Soft Matter Team (https://www.softmatter-l2c.fr/) of the Laboratoire Charles Coulomb in Montpellier, France, under the supervision of Laurence Ramos and Luca Cipelletti, in close collaboration with Christian Ligoure.

Expected starting time: September 2024