Using Breath Figure Patterns on Structured Substrates for the Preparation of Hierarchically Structured Microsieves

Abstract

Microsieves are advanced filtration membranes characterized by a uniform pore size, a high pore density, and a thickness smaller than the pore diameter. The uniform pore size provides a high selectivity; the small thickness gives rise to a high flux and allows efficient removal of any filter cake by backflushing. However, microsieves are sensitive to mechanical stress. Thus, they need either an external macroporous support or a hierarchical structure that provides an integrated supportive structure. We prepare microsieves with a hierarchical pore structure by creating breath figure patterns within layers of solutions of polymers in a volatile solvent that are spread out on top of structured supports. For the formation of breath figure patterns, the volatile solvent is evaporated in a moist atmosphere. This cools the surface to such an extent that dew droplets form on the thin film, partially penetrate into the layer, and create a concave imprint in the final solid polymer layer. This procedure is usually done on flat surfaces; in our case the spreading of the polymer solution is done on a support decorated with protrusions. In this procedure, the dew droplets touch the protrusions of the structured support before the polymer solution vitrifies. At the same time, the trenches of the structured substrate are filled with polymer much deeper than the penetration depth of the dew droplets. After the separation of the vitrified layer from the substrate, we obtain thin polymer membranes with a hierarchical structure consisting of an ultrathin active separation layer with submicrometer pores and a supporting layer with larger pores.

Fabrication of honeycomb-patterned polyalkylcyanoacrylate films from monomer solution by breath figures method

“…Highly ordered micro-porous materials have attracted intensive interest due to their potential applications in biology [1,2], pharmaceuticals [3], tissue engineering [4,5], micrographics [6], optics [7][8][9], and separation [10]. Several strategies such as templating [7,[11][12][13][14][15], self-assembly [16][17][18] and ''breath figures" (BFs) method [19][20][21][22][23][24][25][26], have been developed for fabricating micro-porous materials.…”

Breath Figures: Fabrication of Honeycomb Porous Films Induced by Marangoni Instabilities

“…Miktoarm star copolymers with proper water wettability and mechanical stability have been used to fabricate separation membranes also using ice substrate [131]. Moreover, the breath figures approach has been employed to build polymer membranes on structured substrates in order to obtain hierarchically structured microsieves [208].…”

“…Other examples of nonplanar hierarchically structured porous films are for instance the preparation of membranes for advanced filtration (also known as microsieves) composed by a hierarchical pore structure [208] or the construction of hierarchical structures by combination of electrospinning or electrospraying and breath figures [209][210][211].…”

Polymer Surfaces in Motion

“…Miktoarm star copolymers with proper water wettability and mechanical stability have been used to fabricate separation membranes also using ice substrate [131]. Moreover, the breath figures approach has been employed to build polymer membranes on structured substrates in order to obtain hierarchically structured microsieves [208].…”