Abstract
In this work, we investigate the change of contact angle (CA) of a water droplet during evaporation on a Teflon AF1600 surface in the temperature range between 20 and 80 °C under standard laboratory conditions. An almost constant initial CA and a significant increase of the stabilized CA have been observed. The results reveal a temperature-dependent CA change, mainly due to water adsorption on the solid surface. Soaking experiments indicate that besides adsorption, a temperature-independent friction-like force contributes to the pinning of triple-line and therefore to the CA change. We propose an adsorption coverage parameter and a friction-like force to describe the CA change. Furthermore, we describe a reproducible process to produce smooth and homogeneous Teflon AF1600 thin films, minimizing the influence of roughness and local heterogeneity on the CA.
Highlights
Wettability of a droplet on a solid surface is an essential property of surface science
The water contact angle (WCA) measurement starts after ∼1 s, when the droplet has reached its thermal equlilibrium at the sample surface
We investigated the WCA change during evaporation as a function of temperature and conducted soaking experiments to explore the influence of adsorption
Summary
Wettability of a droplet on a solid surface is an essential property of surface science. While the WCA is decreasing, the friction-like force increases up to its maximum value Ff‐max when the triple-line is depinned and starts moving in CCA mode with the corresponding θsta.
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