Superhydrophobic to Superhydrophilic Wetting Transition with Programmable Ion‐Pairing Interaction

Smart surfaces with switchable wettability are fabricated by using facile surface roughness control with a galvanic cell displacement reaction and attaching polyelectrolyte brushes with quaternary ammonium groups. The reversible switch between superhydrophobicity and superhydrophilicity is achieved by direct counterion exchange. This approach combines well-understood physical and chemical concepts and opens up new applications for external stimuli-responsive smart surfaces.