Designing the topology of ionconducting nano-channels is of paramount interest for applications in separation and catalysis. Dimitri A. Ivanov, Xiaomin Zhu, and co-workers demonstrate on page 3543 how the size and structure of nano-channels can be fine-tuned by using humidity-induced phase transitions in a novel wedge-shaped amphiphile bearing a sulfonate group at the tip. The resulting selfassembled structure can be arrested by photopolymerization to obtain free-standing mechanically stable membranes.