How to Coat the Inside of Narrow and Long Tubes with a Super‐Liquid‐Repellent Layer—A Promising Candidate for Antibacterial Catheters

Abstract Fouling of thin tubes is a major problem, leading to various infections and associated morbidities, while cleaning is difficult or even impossible. Here, a generic method is introduced to activate and coat the inside of meter‐long and at the same time thin (down to 1 mm) tubes with a super‐liquid‐repellent layer of nanofilaments, exhibiting even antibacterial properties. Activation is facilitated by pumping an oxidative Fenton solution through the tubes. Subsequent pumping of a silane solution renders the surface of the tubes super‐liquid‐repellent. The wide applicability of the method is demonstrated by coating stiff and flexible tubes made of polymers, inorganic/organic hybrids, metals, and ceramics. Coated medical catheters show excellent antibacterial properties. Notably, the nanofilaments retain their antibacterial properties even in the superhydrophilic state. These findings open new avenues toward the design of biocide‐free, antibacterial tubings and catheters.