Ion Correlation Enhances Macroscale Boundary Lubrication

While ion correlation is known to enhance molecular-scale solvation forces, its capacity to improve macroscale boundary lubrication on engineering surfaces remains unverified. This study demonstrates that multivalent electrolyte-induced ion correlation significantly reduces macroscopic boundary friction, achieving up to a 67% reduction on alumina surfaces. This macroscopic enhancement is driven by interfacial electrochemical properties, where highly charged polar oxide interfaces trigger strong electrostatic correlation to restructure confined solvents into a rigid, load-bearing barrier. Ultimately, this work proves that interfacial ion correlation directly dictates and enhances macroscale boundary lubrication, bridging molecular-level force control with practical tribological applications.