Inorganic Salt Solution-Based Aerosols for Fabricating Honeycomb-Patterned Porous Membranes

Porous membranes with uniform pore sizes have shown potential applications. Although the breath figure method is renowned for its simplicity, it requires high humidity conditions, presenting challenges in energy consumption and safety, especially in arid climates. This study introduces an approach that uses inorganic salt-based aerosols to successfully fabricate honeycomb-patterned porous membranes at low humidity levels, where pure water vapor cannot produce such structures. Sodium chloride and ferric chloride solutions were used to successfully prepare membranes with pore sizes of ∼5.0 and 1.0 μm, respectively, at a relative humidity of 30%, which effectively separated microspheres of different sizes. The κ-Köhler theory and theories related to bubble bursting mechanisms and aerosols were used to preliminarily analyze the relation between inorganic salt aerosol generation and pore size, demonstrating that an increased NaCl concentration results in small pores. Additionally, potassium chloride and calcium chloride were found to have varying effects on pore size. These findings suggest that aerosols could enhance the applicability of the breath figure method and optimize membrane structures and functionality, thereby achieving broader applications in different fields.