Hybrid wetting state on micro-waffle texturesH. Caps1, 2, D. Vandormael3, J. Loicq3, S. Dorbolo2 and N. Vandewalle2
1 GRASP-Optofluidics, Physics Department, University of Liège - B-4000 Liège, Belgium, EU
2 CSL, Centre Spatial de Liège, University of Liège - B-4000 Liège, Belgium, EU
3 GRASP, Physics Department, University of Liège - B-4000 Liège, Belgium, EU
received 19 August 2009; accepted in final form 23 September 2009; published October 2009
published online 22 October 2009
We have studied the wetting properties of water droplets onto lattices of square micro-cavities. The contact angle has been measured along the triple line and the obtained values have been compared to both Cassie-Baxter and Wenzel models. Despite the large values of the apparent contact angle, the contact line appears to be well pinned on the lattice of square cavities. This leads to anisotropic droplet shapes, reflecting the lattice geometry. Imaging the cavities from below just after drop deposition reveals that the liquid is invading them. The drop is thus in an hybrid state where it presents a large contact angle value while it is sticking on the substrate.
68.08.Bc - Wetting.
47.55.D- - Drops and bubbles.
47.55.np - Contact lines.
© EPLA 2009