Nanofluidics of thin polymer films: linking the slip boundary condition at solid-liquid interfaces to macroscopic pattern formation and microscopic interfacial properties.
If a thin liquid film is not stable, different rupture mechanisms can be observed causing characteristic film morphologies: spinodal dewetting and dewetting by nucleation of holes. This rupturing entails liquid flow and opens new possibilities to study microscopic phenomena. Here we use this process of dewetting to gain insight on the slip boundary condition at the solid-liquid interface. Having established hydrodynamic models that allow for the determination of the slip length in a dewetting experiment based on nucleation, we move on to the quantification and molecular description of slip effects in various systems. For the late stage of the dewetting process involving the Rayleigh-Plateau instability, several distinct droplet patterns can be observed. We describe the importance of slip in determining what pattern may be found. In order to control the slip length, we use polymeric liquids on different hydrophobic coatings of silicon wafers. We find that subtle changes in the coating can lead to large changes in the slip length. Thus, we gain insight into the question of how the structure of the substrate affects the slip length.
Experimental Physics, Saarland University, D-66041 Saarbrücken, Germany.
Joshua D
JD
McGraw
Experimental Physics, Saarland University, D-66041 Saarbrücken, Germany.
Oliver
O
Bäumchen
Experimental Physics, Saarland University, D-66041 Saarbrücken, Germany.
Mischa
M
Klos
Experimental Physics, Saarland University, D-66041 Saarbrücken, Germany.
Sabrina
S
Haefner
Experimental Physics, Saarland University, D-66041 Saarbrücken, Germany.
Matthias
M
Lessel
Experimental Physics, Saarland University, D-66041 Saarbrücken, Germany.
Sebastian
S
Backes
Experimental Physics, Saarland University, D-66041 Saarbrücken, Germany. Electronic address: k.jacobs@physik.uni-saarland.de.
Karin
K
Jacobs
Nucleation; Polymer thin films; Slip; Solid–liquid interfaces; Thin film equations