M/F : PhD thesis in physics

Job Description

Thesis Subject

Interfacial rheology deals with the response of interfaces to deformation and has been the subject of sustained research interest over recent decades. Various devices and methods have been developed to measure the rheological properties of air–liquid interfaces, such as Langmuir cells, various rheometers, and oscillating drop or bubble techniques. Despite the development of these approaches, specific challenges remain in quantifying interfacial properties; some of these techniques are limited to static measurements, and rheological properties are explored only at low frequencies (a few tens of Hz). Recently, we used an atomic force microscope (AFM) to probe the thermal capillary oscillations of a bubble or a hemispherical droplet deposited on a polystyrene surface [1–3]. In this method, the nanometre-scale thermal vibration of the bubble causes the cantilever to move. We have shown that the spectrum of thermal oscillations at the bubble's surface exhibits several resonance peaks corresponding to the bubble's different modes of oscillation.In this experimental research project, we aim to study the rheology of the air/water interface formed by an air bubble immersed in a solution containing ionic surfactants (e.g. sodium dodecyl sulphate, SDS; cetrimethylammonium bromide, CTAB; and 4-(4-dihexadecylaminostyryl)-N-methylpyridinium iodide, DiA). The motion of the bubble or droplet interface will be probed using an atomic force microscope (AFM) cantilever, which will measure the amplitude of the vibrations as a function of frequency. The damping and resonance frequencies of thermal fluctuations will be used to determine the surface tension and surface elasticity of the air/water interface. The frequencies and damping coefficients obtained will be analysed to derive the effective surface rheology (surface tension, surface dilatational viscosity and surface shear viscosity) . The surface charge of the air–water interface, which creates electrostatic barriers and controls adsorption, will be studied in detail. We will vary the salt concentration (e.g. NaCl) in the solutions in order to understand the role of electrostatic shielding on the adsorption dynamics of surfactants.Références : [1] Z. Zhang, Y. Wang, Y. Amarouchene, R. Boisgard, H. Kellay, A. Würger, A. Maali, « Near-field probe of thermal capillary fluctuations of a hemispherical bubble », Phys. Rev. Lett. 126, 174503, (2021). [2] H. Zhang, Z. Zhang, C. Grauby-Heywang, H. Kellay, A. Maali, « Rhéologie de l'interface air/eau étudiée par les ondes capillaires thermiques », Langmuir, 39, 3332, (2023). [3] H. Zhang, B. Gorin, H. Kellay, A. Maali, « Rhéologie viscoélastique d'une solution de polymère étudiée par fluctuation capillaire thermique résonante », Phys. Fluids 35, 121706 (2023).

Your Work Environment

The research area 'Nano-physics of fluids at interfaces' forms part of the 'Soft Matter & Biophysics' team at the LOMA laboratory. The Aquitaine Waves and Matter Laboratory (LOMA) is affiliated with the CNRS and the University of Bordeaux. Its research activities aim to explore and characterise the physical properties of matter by combining fundamental and applied, theoretical and experimental approaches. It enjoys international recognition in the fields of Soft Matter and Condensed Matter Physics, Photonics, Materials Science and Biophysics.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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