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Characterization of stimuli-responsive surfactant and pickering emulsion by means of the pendant drop technique
Microbubble contrast agents and superheated nanodroplets for acoustic vaporization are nowadays collecting much interest due to their promising performance in medical applications such as ultrasound imaging and drug delivery. Those agents are usually coated with a surfactant, which reduces the effective interfacial tension (thereby improving emulsion stability) and affect their dynamic response to ultrasound. Stimuli-responsive surfactants change their properties according to external signals and can be greatly effective in dynamically controlling contrast agents surface characteristics and dynamic. Moreover, the use of solid particles as a substitute for a surfactant can improve the stability of the emulsion.
Keywords: surface tension, pendant drop technique, magnetic surfactant, pickering emulsion
Pendant bubble/drop profile tensiometers are widely used for the determination of mechanical properties at gas-liquid and liquid-liquid interfaces, with very small amounts of sample required. A typical experiment consists in imaging a bubble/droplet created at the tip of a needle (possibly immersed in a solution) with a camera using back-side illumination. The bubble/drop shape is defined by the effect of both the surface tension and gravitational forces. Laplace equation describes the surface curvature of the drop/bubble in relation with the surface/interfacial tension value, which can be used as a fitting parameter in order to obtain its actual value. If a stimuli-responsive surfactant is used to cover the interface, by applying an external signal (i.e., magnetic field) the interfacial tension variation can be detected and quantified.
Pendant bubble/drop profile tensiometers are widely used for the determination of mechanical properties at gas-liquid and liquid-liquid interfaces, with very small amounts of sample required. A typical experiment consists in imaging a bubble/droplet created at the tip of a needle (possibly immersed in a solution) with a camera using back-side illumination. The bubble/drop shape is defined by the effect of both the surface tension and gravitational forces. Laplace equation describes the surface curvature of the drop/bubble in relation with the surface/interfacial tension value, which can be used as a fitting parameter in order to obtain its actual value. If a stimuli-responsive surfactant is used to cover the interface, by applying an external signal (i.e., magnetic field) the interfacial tension variation can be detected and quantified.
The goal of the project is the development of a pendant bubble/drop tensiometry facility with the capabilities of testing stimuli-responsive surfactants and pickering emulsion. The already existing setup in the laboratory will be upgraded in order to improve its precision, introduce temperature control in the test chamber, and to adapt it for measurement under constant and time-varying magnetic fields.
The goal of the project is the development of a pendant bubble/drop tensiometry facility with the capabilities of testing stimuli-responsive surfactants and pickering emulsion. The already existing setup in the laboratory will be upgraded in order to improve its precision, introduce temperature control in the test chamber, and to adapt it for measurement under constant and time-varying magnetic fields.
For further information, please contact Samuele Fiorini via email (sfiorini@ethz.ch)
For further information, please contact Samuele Fiorini via email (sfiorini@ethz.ch)