Wetting morphologies on substrates with striped surface domains

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 theta(gamma) and theta(delta), 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 theta(gamma) is smaller than a certain threshold value theta(ch)(V) which depends only weakly on the volume V and attains the finite value theta(ch)(infinity) in the limit of large V. This asymptotic value is equal to theta(ch)(infinity)=arccos(pi/4)similar or equal to38degrees for all lyophobic substrates with theta(delta)greater than or equal topi/2. For a given value of theta(gamma)