Fabrication of Active Surfaces with Metastable Microgel Layers Formed during Breath Figure Templating.

Patterned porous surfaces with responsive functionalities are fabricated by a thermoresponsive microgel-assisted breath figure (BF) process. When water droplets submerge into a polystyrene (PS) solution during formation of a porous surface by the bottom-up BF process, poly(N-isopropylacrylamide)-co-acrylic acid (PNIPAm-co-AA) microgels dispersed in the solution spontaneously assemble at the water-organic interfaces like "Pickering emulsions", reinforced by capillary flow. The conformal layer of PNIPAm-co-AA microgels lining the pores appears in images from a scanning electron microscope (SEM) either as a smooth surface layer (L) or as an array of domelike protrusions (D), depending on the conditions at which the sample was dried for SEM.