Figure 1
From: Penetration and ligament formation of viscoelastic droplets impacting on the superhydrophobic mesh
Phase diagram of the liquid penetration (a) water, (b) 0.5 g/L, and (c) 2.0 g/L PEO aqueous solution into the superhydrophobic mesh plotted in terms of the Weber number and the mesh pore wide S. The symbols represent different penetration phenomena which are defined in (d–h), symbol (x) shows no penetration. The green dashed line plots the threshold Weber number (Wecr1) for liquid penetration during droplet impact (\({P}_{D}={P}_{c}\)), while the red dashed-dotted line plots the experimental threshold of Weber number (Wecr2) for water droplet recoil penetration. (d–h) Time sequence photos of different types of penetration for (d–f) water droplets and (d–h) the PEO aqueous droplets impact on the superhydrophobic mesh when in (d) water penetrates the mesh during droplet recoiling (W-PR) at V0 = 0.9 m/s; (e) water penetrates the mesh during both droplet spreading and recoiling (W-PSR) at V0 = 1.15 m/s, (f) water penetrated the mesh during droplet spreading (W-PS) at V0 = 1.3 m/s, (g) PEO aqueous droplet penetrates the mesh during both spreading and recoiling (PEO-PSR) at V0 = 0.58 m/s and PEO concentration 0.5 g/L; (h) PEO aqueous droplet penetrates the mesh only during spreading (PEO-PS) at V0 = 1.39 m/s and PEO concentration 3 g/L, the ligament retract back to their mother droplets. The penetration during the spreading and recoiling are denoted by blue and pink arrows, respectively. The scale bars in (d–h) are 1.0 mm. (i) Schematic diagram of the symmetry cavity collapse for water droplet observed at 4.6–5.2 ms in (d). (j) Schematic diagram of the cavity detachment observed for PEO aqueous solution at 4.0–5.25 ms in (g).
