Figure 4
From: Controlled droplet transport to target on a high adhesion surface with multi-gradients
(a) Droplet movement behaviours on the graphite plate with V-shape wettable gradient and corresponding force analysis. Two separate droplets (marked as 1, 2) can spread closely to each other and merge into one if the distance between two droplets is short. The driving force arises from wettable gradient force (Fwg). (b) Droplet movement behaviours on the graphite plate with V-shape wettable gradient and rhombus-shape pattern and corresponding force analysis. Two droplets (marked as 1′, 2′) move toward to each other and then merge quickly into one even the distance between two droplets is much longer, which is due to the cooperation of three driving forces, i.e., wettable gradient force (Fwg), Laplace pressure force (FL) and wettable different force (Fwd). (c) Water droplet movement behaviours on a surface with unidirectional gradients and Laplace pressure. (d) Water droplet movement behaviours on a surface with V-shaped gradients and Laplace pressure. The results show that a droplet can move unidirectionally on a surface with unidirectional gradients and two water droplets (marked as 1, 2) move towards each other and merge into one on a surface with V-shaped gradients, even when the as-prepared surface is turned upside down. The scale bar is 2 mm.
