(a) Experimental apparatus. (b) Plunging wafers into liquid bath with/without air entrainment, where the empty arrows indicate downward motion of plates. Left part: smooth wafer is plunged into water–glycerol solution with speed U p ≈ 0.23 (m/s), and contact line is stable. Right part: horizontally grooved wafer is plunged into the same solution with U p ≈ 0.2 (m/s), where contact line front is unstable. Solid arrow and circle denote bubble shot from apex of distorted contact line and “rewetting” bridges, respectively. (c) Geometries of etched microstructures on silicon wafer surfaces: cylindrical pillars (upper) and grooves (lower).