Fig. 5
From: Wetting transitions in droplet drying on soft materials
Mechanism of dynamically triggered wetting transition. a Schematic showing a contact line pinned on a sharp quasi-static apex and the definitions of the apparent contact angle, θ*, the angle between the liquid–solid interface and the horizontal, ψ, and the angle between the liquid–vapor and liquid–solid interface, θ. At contact line depinning, the condition θ = θr has to be satisfied. The black line is a piecewise polynomial fit of fifth order. Theoretical receding contact angle, \(\theta _{{{\mathrm{r,qs}}}}^ \ast\) (empty diamonds), and θ* (filled diamonds) vs. t for a contact line pinned on a quasi-static apex for b slow evaporation (rH = 90%, droplet from Fig. 3a) and c rapid evaporation (rH = 15%, droplet from Fig. 3d) of a droplet on a compliant substrate. d Difference between the apparent contact angle, θ*, and the theoretical receding contact angle if the wetting ridge acts as a quasi-static defect, \(\theta _{{{\mathrm{r,qs}}}}^ \ast\), as a function of |dR/dt|Eτ/γLV. We tested two material compositions of Silicone CY 52–276, ratio 5:6 (orange, N = 4, with 24 time steps) and ratio 9:10 (red, N = 5, with 38 time steps), with rH of 15 ± 1% and 90 ± 1% and at room temperature (T = 24 °C). The gray dashed line is a logarithmic fit with three parameters. Scale bar: a 5 µm (with an aspect ratio of 1:1). Source data are provided as a Source Data file for (b–d)
