ESPCI web site
The “École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris” (ESPCI Paris PSL) is a “Grande École d’Ingénieurs” with a strong international reputation for research (6 Nobel Prizes) and a member of the Université PSL (Paris Sciences & Lettres).
ESPCI is a highly multidisciplinary environment with teaching and research in physics, chemistry, and biology.
Research Project. Most solid/liquid interfaces are characterized by a net spatial separation of charges, due to the dissociation of surface charges on the solid surface, which get screened by a diffuse layer of counter-ions in the liquid [1].
The dynamics of this “Electric Double Layer” of typical nanometric size, has fundamental importance for diverse domains such as energy storage (super-capacitors, batteries), energy harvesting, or nanofiltration…
However, the dynamic couplings between ionic charge transport and liquid flow at these interfaces (“electrokinetic effects”) remain poorly understood, with e.g. long-standing discrepancies between static and dynamic surface charges [2], controversial reports of flow-induced shift of the surface charges [3] or peculiar “electro-viscous” over-dissipation during deformation of the electric double layer [4].
These observations call for the development of novel experimental methodology to quantitatively probe the dynamic response of charged solid/liquid interfaces. The aim of this PhD is to investigate the full out-of-equilibrium response of the ionic double layer over decades of dynamic range, by developing new dynamic Atomic Force Microscopy methodology, based on Tuning-Fork AFM. These techniques have recently demonstrated their potential for the investigation of the nano-rheology of non-volatile liquids [5], [6] and will be here adapted to study dynamic process in aqueous solutions. In particular, we will probe the dynamic response of these charged interfaces under the flow induced by an oscillating colloidal probe, to extract the full conservative and dissipative rheological response associated with the deformation of the double layer, and gain novel insights on the coupled electro-kinetic effects taking place at the interface. These measurements will be carried out by systematically varying the physicochemistry of the aqueous solution, and the properties of the solid surfaces, ultimately shedding new lights on the molecular processes taking place at the intimate scale of the solid/liquid interface. We will finally probe how electronic capacitive couplings between the tip and the surface can affect interfacial ionic dynamics. The PhD student will acquire expertise in nano-assembly and micro-fabrication, signal processing for dynamic Atomic Force Microscopy, as well as fundamental knowledge of electrokinetic effects at solid/liquid interface, of relevance for a broad class of micro and nanofluidic problems of interest.
[1] L. Bocquet and E. Charlaix, “Nanofluidics, from bulk to interfaces,” Chemical Society Reviews, 2010.
[2] R. Hartkamp, A. L. Biance, L. Fu, J. F. Dufrêche, O. Bonhomme, and L. Joly, “Measuring surface charge : Why experimental characterization and molecular modeling should be coupled,” Curr. Opin. Colloid Interface Sci., 2018.
[3] D. Lis, E. H. G. Backus, J. Hunger, S. H. Parekh, and M. Bonn, “Liquid flow along a solid surface reversibly alters interfacial chemistry,” Science, 2014.
[4] F. Liu, A. Klaassen, C. Zhao, F. Mugele, and D. Van Den Ende, “Electroviscous Dissipation in Aqueous Electrolyte Films with Overlapping Electric Double Layers,” J. Phys. Chem. B, 2018.
[5] J. Comtet, G. Chatté, A. Niguès, L. Bocquet, A. Siria, and A. Colin, “Pairwise frictional profile between particles determines discontinuous shear thickening transition in non-colloidal suspensions,” Nature Communication, 2017.
[6] J. Comtet, A. Niguès, V. Kaiser, B. Coasne, L. Bocquet, and A. Siria, “Nanoscale capillary freezing of ionic liquids confined between metallic interfaces and the role of electronic screening,” Nature Materials, 2017.
Knowledge and skills :
The student will acquire expertise in nano-assembly and micro-fabrication, signal processing for advanced dynamic Atomic Force Microscopy, as well as fundamental knowledge of dynamic transport at solid/liquid interface, of relevance for a broad class nanofluidic problems of interest.
We are thus looking for a student strongly motivated by innovative experimental work, with a background in physics.
Supervisor : Jean Comtet (jean.comtet@espci.fr)
How to apply :
Applications (include CV and grades) should be sent to Jean Comtet (jean.comtet@espci.fr)
Start date and duration : 01/10/2023, with a duration of 3 years.