Experimental study on the dynamic wetting of silica nanofluids

Abstract

Nanofluids are recently discovered nanomaterials with improved thermophysical properties that can enhance the efficiency and reliability of heat transfer systems. Their relevant properties for describing heat transfer, thin film flows, droplet impingements, or microfluidics are surface tension and wettability. A thorough investigation on this topic of research is crucial to understand the root cause of the factors affecting the degree of wetting of nanofluids on solid surfaces. In the present work, silica (SiO2) nanofluids with different mass fractions and types of surfactants based on deionized water were prepared using a simple and cheap two-step method. The effect of surface tension changes on the lateral friction force of the nanofluid was studied using a solid–liquid interface lateral friction force detection system. According to the findings, an increase in the mass fraction of silica nanoparticles led to the larger surface tension of the nanofluid, resulting in a linear decrease in the lateral friction of the latter on the hydrophobic surface of PDMS. The use of ionic surfactants as dispersants caused a dramatic decrease in surface tension and static angle of SiO2 nanofluid (by 20% and 30% after adding SDS and by 40% and 50% after adding CTAB, respectively). This exerted a noticeable impact on the lateral friction force of the fluid. On the contrary, polymeric surfactants (NaPSS) had a small effect on the lateral friction of SiO2 nanofluid. Meanwhile, the lateral friction after stable motion differed from the maximum static friction to a small extent.