Jean Comtet

Research Associate at CNRS (Chargé de recherche CNRS)
Laboratory for Soft Matter Science and Engineering
ESPCI, Paris

We are looking for motivated Master’s student to join the group!
Two internship proposals are available, with possible extensions as PhDs.

– Nanoscale Solid Friction in Confined Aqueous Systems: an Application to Cement-like Rheology. M2 + funded PhD position (collaboration with Saint-Gobain Research).

The objective of this internship is to gain new experimental insights on the mechanical interactions (friction, adhesion…) in nanoconfined solid contacts in aqueous electrolytic solutions. The general context is to understand what sets these interactions in macroscopic construction materials (e.g. cement paste), where extreme physicochemical conditions (high molarity, high pH, ion-specific effects…) leads to poorly understood physics. To do so, we will rely on advanced Atomic Force Microscopy techniques to probe friction between micrometric silica colloids in various aqueous solutions. We will explore in particular the role of the local frictional history on the contact strength, related to poorly-understood “aging” effects, and their relation to ion-specific effects (e.g. why do Ca2+ ions seem to act as a glue in these ultra-confined contacts?!).

– Experimental Molecular Dynamics : Can we watch how individual liquid/polymeric molecules move close to a solid surface?

When confined to nanometric scales, liquids can show a range of peculiar behaviors, such as molecular ordering, reduced friction leading to fast flow, change of their relaxation dynamics, etc.. All of these effects are intimately related to short-range interactions arising in the presence of the solid surfaces. However, our understanding of liquid matter at interfaces remains poorly understood, due to the lack of tools able to directly image the dynamics of liquid molecules at surfaces and in confinement. The idea of this internship is to develop novel experimental approaches to directly image in real space how single liquid molecules move close to solid surfaces, so far the exclusivity of molecular dynamics simulations!


I am an experimental physicist, working as a CNRS researcher at ESPCI, Paris, France and based in SIMM Laboratory (Laboratory for Soft Matter Science and Engineering).

My research focuses on the physical, physicochemical and dynamic properties of interfaces and materials, and is characterized by interdisciplinary approaches, at the crossroad of soft matter, physics, mechanics, optics and nanosciences.

In particular, I use and develop innovative experiments, based on mechanical or optical techniques (Atomic Force Microscopy, Surface Force Apparatus, Super-Resolution and Single-Molecule microscopy, Mechanophore Optical Probes…), to investigate the properties of interfaces and materials at the nanometric and molecular scales.

Probing these ultimate scales allows me to reveal specific and original behaviors (nanorheology of ionic liquids in confinement, liquid-like behavior of subnanometric gold junction, proton surface transport at the single molecule scale…) as well as rationalize the behaviors of macroscopic heterogeneous materials (role of contact forces in shear-thickening suspension rheology, nano-rheology of the interfacial liquid film when sliding on ice, role of molecular chain damage in macroscopic elastomeric network mechanics…).

Feel free to get in touch 🙂