Formation of residual droplets upon dip-coating of chemical and topographical surface patterns on partially wettable substrates

We have studied the occurrence of residual liquid induced by the presence of defects during dip-coating of partially wettable surfaces. The defects are either topographical in nature such as surface protrusions or depressions, or chemically defined surface energy heterogeneities. Typically the residual liquid is distributed in a cascade of satellite droplets that arise from capillary break-up and the recession of the coating meniscus, after it is temporarily pinned by the defect. We characterize the volume and position of the largest satellite droplet as a function of the geometrical shape and size of the defect as well as its topographical amplitude or contact angle contrast. Our results are relevant for instance to immersion lithography, where the occurrence of residual droplets is undesirable. (C) 2020 Elsevier Ltd. All rights reserved.