Measuring ∆ cos θ and friction force. While we do not observe significant differences in r s and r max measurements for Glaco and Black Si (See Figures and and), the two surfaces nonetheless have very different droplet-solid friction F fric . For millimetric-sized droplet, contact-line pinning results in F fric = 0.15 and 5 µN for Black Si and Glaco, respectively (Fig. ).