Injectable and Self-Healing MXene-Reinforced pH-Responsive Hydrogel: Realizing Low-Friction and Durable Lubrication

Hydrogels are ideal lubricants due to their hydrophilicity and ability to mitigate issues such as creep and leakage. Based on the diversity of application environments, it is crucial to develop hydrogels with adjustable lubrication that can adjust their lubrication properties by changing in the external environment. However, they still face challenges in balancing responsiveness, lubrication efficacy, and safety. This study presents a pHresponsive hydrogel prepared from polyvinylpyrrolidone and phytic acid, with the addition of MXene and glycerol to enhance its tribological performance. The optimal contents of MXene and glycerol for peak lubrication efficiency are found to be 5 mg/mL and 5 wt %, respectively. This hydrogel lubricant can maintain a low-friction state without failure in long-term testing for 3 h, achieving a coefficient of friction (COF) of 0.01. The synergistic lubrication effect of MXene and glycerol reached a friction reduction of 69% and a wear resistance improvement of up to 96%. Moreover, the COF can be regulated by adjusting the pH value. This hydrogel also stands out with its robust self-healing, injectability, and biocompatibility, making it an excellent candidate for advanced lubrication in biomedical applications.