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Pickering emulsion is a new type of stable emulsion made by ultrafine solid particles instead of traditional surfactants as stabilizers, which has received widespread attention in recent years. The preparation methods of stator-rotor homogenization, high-pressure homogenization, and ultrasonic emulsification were compared with others in this work. The main factors affecting the stability of Pickering emulsion are the surface humidity of the solid particles, the polarity of the oil phase, and the oil–water ratio. These factors could affect the nature of the solid particles, the preparation process of Pickering emulsion, and the external environment. Consequently, the long-term stability of Pickering emulsion is still a challenge. The tribological investigations of Pickering emulsion were summarized, and the multifunctional Pickering emulsion shows superior prospects for tribological applications. Moreover, the latest development of Pickering emulsion offers a new strategy for smart lubrication in the near future.

In the pressent work, nanosized poly (N-isopropyl acrylamide) (PNIPAM) microgels were prepared and used as lubricant additives in bovine calf serum (BCS) for titanium alloy/ultra-high molecular weight polyethylene contact. The effects of sliding speed, load, and temperature on the lubrication behavior were studied on a pin-on-disc tribometer. The tribological results showed that the PNIPAM microgels can significantly improve the lubricity of BCS solution. The PNIPAM microgels exhibited notable temperature-sensitive lubrication characteristics. When the temperature was close to the low critical solution temperature of the PNIPAM microgels, the contact had the lowest friction coefficient due to the formation of a good lubricating layer with collapsed microgels and proteins. This discovery contributes to establishing a new strategy for friction-reduction and antiwear of titanium alloy artificial joint materials.