[交流] 法国波尔多大学 LOMA实验室 公派读博-2021 zhangzaicheng8911@163.com

Air/water surface rheology using Near-Field Probe of thermal capillary wave Supervisor : Abdelhamid Maali    e-mail:abdelhamid.maali@u-bordeaux.fr      Tel:0540008365 Interfacial rheology of fluids interfaces decorated by surface-active species such as surfactants, proteins, or particles has many importance since it controls foams and emulsion stability, and it has many applications such as for oil recovery, microelectromechanical system as well as biomedical. Interfacial rheology deals with the response of interfaces against deformations, it has been the subject of research interest during the last decades. A range of devices and methods have been developed to measure the rheological interface properties, such as Langmuir troughs, various rheometers  and oscillating drop or bubble . Despite the development of these different, we still face specific challenges to quantifying the interfacial properties; some of this techniques are limited to static measurements and rheological properties are only probed at low frequencies (a few tens of Hz). The dynamic atomic force microscope (AFM) is a powerful tool to investigate structure and rheology of confined liquids, and its dynamic mode allows to separate viscous and elastic forces [1-2].  Recently we have used an atomic force microscope to probe the thermal capillary oscillation of a hemispherical bubble deposited on polystyrene surface [3]. In this method, the nano-metric thermal vibration of the bubble drives the motion of the cantilever. We have shown that the spectrum of the thermal oscillations of the bubble surface presents several resonance peaks corresponding to the different mode of shape oscillations. In this thesis, we intend to probe the rheology of the air/water interface formed by air bubble immersed in solution contaning surfactants (example:sodium dodecyl sulfate, SDS) . The motion of the bubble interface will be probed using an AFM cantilever that measures the amplitude of the vibration versus frequency. The damping and the resonance frequencies of the thermal fluctuations will be used to measure the surface tension and surface elasticity of the bubble surface. During the thesis, we will determine the resolution of the method and the range of parameters where it works efficiently, and compare with existing techniques. The solubility of the surfactants molecules could be an important parameter distinguishing among amphiphilic molecules, soap molecules from phospholipids or steroid alcohols, and it will be studied in details.

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