Wetting Properties of Natural and Plasma-Processed Biomimetic Surfaces - Biomimetic Architectures by Plasma Processing - page 122

to Wenzel transition for a droplet hitting the surface of micro-
patterned Si coated with PF

. They took snapshots of a droplet
with 1 mm radius hitting the surface shown in Fig. 4.8a. The impact
velocity was calculated just prior to the droplet hitting the surface.

3

(a)

(b)

Figure 4.8 (a) Snapshots of a droplet with 1 mm radius hitting a patterned

surface. The reported impact velocity is that just prior to the
droplet hitting the surface. The bouncing and pinning of the
droplet on this surface with 5 µm diameter, 10 µm height, and
10 µm pitch pillars occurred at an impact velocity of (i) 0.44
m s -1 and (ii) 0.88 m s -1 , respectively. (b) Measured critical
impact velocity of a droplet with 1 mm radius as a function of
geometric parameters (triangles, experimental; 5 µm diameter
and 10 µm height pillars). The data are compared with the
criterion of impact velocity for pinning of the droplet (solid
line, predicted) for patterned Si with different pitch values.
Reprinted with permission from Ref. [29], Copyright © 2007,
John Wiley and Sons.