Adhesion Mechanism of Water Droplets on Hierarchically Rough Superhydrophobic Rose Petal Surface
Figure 5
Contact angle and contact diameter of evaporating water droplets on the fresh and dried rose petal surface. The contact angle remains high on the low-adhesive dried petal because the contact diameter shrinks quite freely with the decreasing droplet volume, but on the high-adhesive fresh petal it decreases quite fast because the contact diameter remains pinned (a). The shrinking of the contact diameter begins when the droplet volume on the dried surface is still over 5 μL, but on the fresh surface it does not begin until the volume is less than 3 μL (b). Because of the decreasing contact diameter, the receding contact angle remains approximately constant between the droplet volumes of 2 and 1 μL, and is and on the dried and fresh petal, respectively (c).
