SKM 2023 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 34: Wetting, Droplets and Microfluidics I (joint session DY/CPP)

CPP 34.10: Talk

Wednesday, March 29, 2023, 12:30–12:45, ZEU 148

Fingering contact propagation between a droplet and a thin liquid film — •Kirsten Harth — Fachbereich Technik, TH Brandenburg — MRTM und MARS, Otto von Guericke Universität Magdeburg

When impacting droplets approach a hard plane substrate slowly, so that the Weber number is below approximately 5, a contact-less rebound will occur due to the entrainment of ambient gas. On slightly deformable and smooth spin-coated liquid films upon a rigid solid, this effect is more robust and may occur until slightly higher Weber numbers. Deformation of the thin film is usually ignored while it is proven to be present. The deformation amplitude depends on the impact dynamics as well as the thickness and viscosity of the surficial oil layer. At slightly higher impact velocities, i.e. slightly higher Weber numbers, delayed contact formation between the film liquid and the droplet occurs. Depending on the layer properties, interestingly, the contact line may be unstable displaying a fingering texture. Instability occurs independently of whether the drop and film liquid differ or not. We present and analyze this phenomenon.