Wetting morphologies on substrates with striped surface domains

Abstract

The wetting and dewetting of chemically structured substrates with striped surface domains is studied theoretically. The lyophilic stripes and the lyophobic substrate are characterized by different contact angles θ γ and θ δ , respectively. We determine the complete bifurcation diagram for the wetting morphologies (i) on a single lyophilic stripe and (ii) on two neighboring stripes separated by a lyophobic one. We find that long channels can only be formed on the lyophilic stripes if the contact angle θ γ is smaller than a certain threshold value θ ch (V) which depends only weakly on the volume V and attains the finite value θ ch (∞) in the limit of large V. This asymptotic value is equal to θ ch (∞)= arccos (π/4)≃38° for all lyophobic substrates with θ δ ⩾π/2. For a given value of θ γ <θ ch (∞), the extended channels spread onto the lyophilic stripes with essentially constant cross section.