Fig. 3.

Droplet spreading on flexible substrates. (A) Image sequences of droplet ($D_0=$ 2.91 mm) impacting on flexible and rigid hydrophobic substrates (steel beam treated with nC2). The maximum spreading diameter is indicated on the images as $D_{max}$. (Scale bar, 1 mm.) (B) Spreading parameter ($D_{max}/D_0$) for different values of $We$. Lines indicate the predicted values for $D_{max}/D_0$ using three theoretical models for their validity range: Clanet et al. (6) (dashed line), Laan et al. (28) (dash-dotted line), and Mao et al. (40) (dotted line). $P_e$ of the impacts is indicated by the second horizontal axis. (C) $D_{max}/D_0$ plotted vs. $W{e}_m$ for the rigid (circle) and flexible cases for two droplet sizes (triangle, $D_0=$ 2.91 mm; square, $D_0=$2.32 mm). Sample size ($n$) for B and C is five repetitions per point. Error bars represent ±99% confidence interval of the mean. Nonvisible error bars are smaller than the marker size.