Utilizing Interparticle Interaction for Magneto-Viscosity, -Wettability, and -Tribology Control in Liquid-Metal-Based Magnetic Nanofluids

Liquid-metal-based magnetic fluids (LMMFs) present a promising avenue for developing intelligent, magnetically responsive lubricants deployed under extreme conditions. However, fundamental understanding of their surface (e.g., wettability) and interface (e.g., viscosity and tribology) behavior remains elusive. Herein, we report a systematic study of a nanoengineered LMMF system comprising Fe₃O₄ and Mo nanoparticles in a Ga-In-Sn eutectic matrix and elucidate its magneto-viscosity, -wetting, and -tribological performance with these nanophases' contribution under magnetic fields. Our thermodynamic validation confirms active interactions at the Mo-Fe₃O₄ interface. With this interaction, we reveal LMMF's magneto-viscosity change by nanophase chain formation, provide a theoretical Gibbs free energy analysis, and innovatively link this knowledge to understand the magneto-wetting transition governed by this chain formation and interfacial pinning effects. More excitingly, magneto-tribological performance is also dominated by the competition between chain formation and nanoparticle motion under magnetic field and tribological loading. This investigation of magneto-viscosity, -wetting, -tribological performance, and their linkage implies a novel way to manipulate wetting and friction contact. The coupled understanding of magnetic, thermodynamic, interfacial, and tribological responses of LMMF enables predictable wetting and rubbing states and offers a promising field-controllable lubrication via critical noncontact magnetic manipulation in tribology applications.