Surfactant assisted and in situ formed micro liquid metal as excellent lubricant additive in polyimide coating

Liquid metal (LM) can be well distributed in polyimide (PI) coatings by ultrasonic shear into 1–2 μm diameter. The LM incorporated PI (PI-LM) coatings show remarkably enhanced tribological properties when the coating slide against GCr15 steel ball at room temperature, while the mechanical properties are slightly reduced. When the filling amount is 8%, the wear is just 10% of pure PI and the friction coefficient can be reduced by 31.6%. During friction process, the LM microspheres are squeezed to the frictional interface and form a transfer film together with PI debris, achieving lower wear and friction coefficient. These results show that PI-LM coatings have high potential as advanced self-lubricating materials.