The wetting and spreading of nanofluids on solids: Role of the structural disjoining pressure

The wetting and spreading behavior of pure liquids over solid surfaces changes if liquids contain nanosized spherical particles or surfactant micelles, globular proteins and macromolecules. Recent studies on the spreading of nanofluids have demonstrated the inadequacy of well-known concepts of the spreading and adhesion of pure liquids on solid surfaces in understanding nanofluid spreading behavior. This paper reviews the progress made in the wetting and spreading of nanofluids over solid surfaces with an emphasis on the complex interactions between the particles in the nanofluid and with the solid substrate, as well as the spreading of thin nanofluid films containing nanoparticles on hydrophilic surfaces driven by the structural disjoining pressure gradient. The spreading droplet advances as a series of distinct nanoparticle layers.