Fig. 4: Estimation of normalised driving force \(\tilde{F}\), as well as contact angles \(\theta^{\rm{{eff}}}_{\rm{{wa|s}}}\) and \(\theta^{\rm{{eff}}}_{\rm{{wa|o}}}\), for water and ethylene glycol droplets on structured surfaces imbibed with various lubricants.
From: Bidirectional motion of droplets on gradient liquid infused surfaces
Each point is the average of five apparent contact angle θapp measurements of sessile droplets at a given solid fraction fs. The surrounding coloured area represents the standard deviation. Dashed lines are fits of Eq. (13) using the least-square method. The gradient of the fits corresponds to \(\tilde{F}\), while extrapolations of those fits to fs = 1 and fs = 0 give a measure of the values of the cosine of droplet contact angle on pure solid, \(\cos {\theta }_{{\rm{wa}}| {\rm{s}}}^{{\rm{eff}}}\), and on pure lubricant, \(\cos {\theta }_{{\rm{wa}}| {\rm{o}}}^{{\rm{eff}}}\), respectively.
