Structural disjoining pressure induced solid particle removal from solid substrates using nanofluids.

Nanofluids comprising nanoparticle suspensions in liquids have significant industrial applications. Prior work performed in our laboratory on the spreading of a nanofluid on a solid substrate has revealed that the structural disjoining pressure gradient caused by the layering of the nanoparticles normal to the confining plane of the film with the wedge profile is a new mechanism for oily soil detachment from the solid substrate. In the present work, we explore the application of this new mechanism for the solid particle detachment using latex particles on glass and a copper-coated wafer substrate using nanofluids. In the experiment, we employed the nanofluids to observe the detachment of the latex particles adhered to the glass substrate. We found that the structural disjoining pressure exerted by the nanoparticles can detach the solid particles on the glass substrate. A video depicting this mechanism is provided. Our results showed that the detachment of the particulate solid particles on the solid substrate was clearly enhanced by the nanofluids, compared to using only pure liquids (such as water). The detachment efficiency was increased with the increase in the nanoparticle volume fraction. Our nanofluids also showed a greater detachment efficiency for the particulate soil removal from the copper-coated wafer substrates compared to that of pure liquids. We found that the detachment efficiency is well correlated with the calculated structural disjoining energy. Our findings in this paper provide new insights for the novel application of the structural disjoining energy mechanism for cleaning hard surfaces.