Electroactive TiO₂-Cu nanotube platform with synergistic charge modulation and Cu²⁺ release for marine antifouling

Biological damage remains a critical limiting factor that hinders the application of highly biocompatible titanium alloys in marine engineering. Exploiting the delicate electrostatic interactions at the interface between organisms and nanomaterials is of vital importance. In this study, an external direct current was applied to copper-coated capacitive TiO₂ nanotubes (TNT-Cu) to evaluate the antifouling effect on sessile biofilms and planktonic bacteria, and to elucidate the underlying mechanisms. The heterostructure exhibited high specific capacitance and superior antifouling performance. Upon electrochemical charge-discharge, TNT-Cu achieved 98.3 ± 0.9 % adhesion inhibition and 96.0 ± 2.0 % algicidal activity against Phaeodactylum tricornutum. The charged TNT-Cu achieved synergistic antifouling through surface charge-induced electrostatic sterilization and controlled Cu²⁺ release. Physiologically, the electrical interaction combined with Cu²⁺ significantly disrupted algal electron transport, induced reactive oxygen species (ROS) accumulation, and caused membrane rupture. This work provides a promising, durable, and eco-friendly antifouling strategy for marine applications of titanium-based materials.