SPP 2171 Workshop: "Wetting of Flexible, Adaptive, and Switchable Substrates"

We study the wetting of adaptive substrates using a mesoscopic hydrodynamic
model for a liquid droplet on a polymer brush, refining the model in [1]. First, we
show that Young’s law still holds for the macroscopic equilibrium contact angle
and that on the mesoscale a Neumann-type law governs the shape of the wetting
ridge (comparable to the case of elastic substrates [2]). Further, we numerically
examine the wetting ridge dynamics for a moving meniscus, i.e., we consider an
“inverse Landau-Levich geometry” where a brush-covered plate is introduced
into a bath. We find stick-slip motion in good qualitative agreement with exper-
imental observations [3,4] and discuss criteria for the onset of the corresponding
instability.
[1] U. Thiele and S. Hartmann, Eur. Phys. J.-Spec. Top., 2020, 229, 1819-1832.
[2] B. Andreotti and J. H. Snoeijer, Annu. Rev. Fluid Mech., 2020, 52, 285-308.
[3] S. Schubotz et al., Adv. Colloid Interface Sci., 2021, 294, 102442.
[4] L. Wan, X. Meng, Y. Yang, J. Tian and Z. Xu,Sci. China Chem., 2010, 53,
183-189.