Congratulations on the defense of Robin Götzelt’s diploma thesis

On January 24, 2025, Robin Götzelt successfully defended his diploma thesis entitled “Experimental study of liquid film thinning behavior using interferometry” at our Chair of Transport Processes at Interfaces.

Material separation processes that use foam such as foam fractionation and flotation, have gained industrial focus because of their ability to gently separate substances based on their hydrophobicity. As thin liquid films constitute foam and its behavior, the fundamentals of their optical measurement and the physics of their thinning dynamics are presented in this work. A new interferometric method capable of studying the thickness of single, purely liquid films ranging from 100nm to over 5000nm has been developed, complementing existing methods that operate at thicknesses below 100nm.

The new algorithm is validated through simulation and its sensitivity to imposed errors is estimated, from which measures for increased robustness are derived. The behavior of thin liquid films with various surfactants is experimentally studied at different surfactant and salt concentrations. The results indicate the proper functioning of the new method but also that the liquid’s composition has the most significant effects at thicknesses below 100nm. Suggestions are made on how more complex film geometries can be analyzed and which advancements of the physical setup are appropriate.