  Macro-textured superhydrophobic surfaces can reduce droplet-substrate contact
times of impacting water droplets, however, surface designs with similar
performance for significantly more viscous liquids are missing, despite their
importance in nature and technology such as for chemical shielding, food
staining repellency, and supercooled (viscous) water droplet removal in
anti-icing applications. Here, we introduce a deterministic, controllable and
up-scalable method to fabricate superhydrophobic surfaces with a 3D-printed
architecture, combining arrays of alternating surface protrusions and
indentations. We show a more than threefold contact time reduction of impacting
viscous droplets up to a fluid viscosity of 3.7mPa s, which equals 3.7 times
the viscosity of water at room temperature, covering the viscosity of many
chemicals and supercooled water. Based on the combined consideration of the
fluid flow within and the simultaneous droplet dynamics above the texture, we
recommend future pathways to rationally architecture such surfaces, all
realizable with the methodology presented here.
