Polymeric microstructure arrays consequence of Marangoni flow-induced water droplets

This paper describes a cost-effective approach to fabricate intricate arrays of polydimethylsiloxane (PDMS) and polymeric microstructures based on porous polystyrene (PS) films generated from arrays of water droplets. To start, a thin layer of ethanol film is exposed to a humid air flow. Upon the evaporation of ethanol and simultaneous condensation of water as the ethanol phase recedes, a Marangoni flow causes the flow of liquid from the ethanol phase into water fingers emerged along the receding contact line, which finally detach to form ordered water droplet arrays behind the receding contact line. The water droplet arrays are subsequently used as templates to generate porous PS films. The porous PS films are then used as sacrificial layers and masters to fabricate various arrays of PDMS dots and PDMS stamps with posts, respectively. The PDMS stamps containing various microstructures are further utilized to create polymer rings, PDMS dots, porous PDMS films, and PDMS aperture rings, and for contact printing of patterns of self-assembled monolayers.