Anomalously Stable, pH-Responsive, and Biocompatible Water-in-Extreme-Pressure Agent Emulsions with Enhanced and Tailorable Tribological Performances

Stimulus-responsive emulsions are ideal platforms for developing smart and clean liquid lubricants in view of their combined lubricating and cooling performances as well as good sustainability for achieving compositional separation and recycling. Nevertheless, current design strategies normally require complicated formulations and relatively high-cost and time-consuming preparations to fulfill the functional requirements for industrial tribological applications. Here we illustrate a paradigm for creating emulsion-based lubricants with long-term stability, convertible emulsification/demulsification, high and enduring lubricity, and tailorable friction and wear resistance simply by mixing a commercially available liquid extreme-pressure agent, which can provide lubrication and load-carrying capacity via tribochemical reactions with steel surfaces, with deionized water that can enhance its tribological properties by introducing additional heat dissipations using a commercially available anticorrosion agent capable of yielding low interfacial tensions and a pH-controlled emulsifying capability. Together with their excellent biocompatibility and scalability, our prepared water-in-extreme-pressure agent emulsions can serve as one kind of economical, safe, and smart liquid lubricant product.