Interfacial Transport Persistence Governs the Ion Tolerance of Self-Diffusiophoretic Colloidal Motors

Chemically driven colloidal motors hold immense promise for biomedical applications, yet they inevitably suffer from severe motion degradation in high-salt physiological environments, because electrostatic screening compresses the electrical double layer (EDL) and suppresses interfacial transport. Here, we show that hydrophobic interfacial engineering enables robust propulsion of Pt–SiO₂ colloidal motors under ionic conditions where conventional hydrophilic motors become nearly inactive. Molecular dynamics (MD) simulations reveal that the hydrophobic interface sustains effective H₂O₂ transport within the compressed interaction layer, thereby maintaining the nonequilibrium flux required for self-diffusiophoretic propulsion. Guided by these observations, we establish a dynamic interfacial response framework that quantitatively describes the coupling between electrolyte screening, interfacial transport, and propulsion. The model accurately reproduces the experimentally observed salt-dependent velocities. Our results reveal that propulsion degradation is not determined solely by Debye-layer compression, but by whether nonequilibrium interfacial transport can persist within the compressed region. These findings identify interfacial transport persistence as a key principle governing ion tolerance and provide new guidelines for the design of active colloidal systems in complex ionic environments.