Study on the Mechanism of the Nanofluid Wetting Inversion Effect Enhancing the Flow in Microchannels

Nanofluids can induce a reversal of wetting at the solid–liquid interface, which is expected to enhance flow within channels. In this paper, we evaluate the performance of nanofluids in inducing wetting transitions on solid surfaces and investigate the mechanisms that improve flow. First, the experimental tests on contact angles demonstrate that solid surfaces treated with surfactant–nanoparticle composite solutions exhibit high hydrophilicity. The effects of nanoparticles and surfactants on reducing the contact angle are separately investigated. The basic mechanism of solid–liquid interface oil film separation caused by the separation pressure is elaborated. To verify the promoting effect of wetting reversal on flow, we conducted flow testing experiments using a self-designed 3D microchannel model. The mechanism by which the wetting reversal effect of nanofluids in microchannels affects flow efficiency, flow trajectory, and distribution of the flow medium volume is elucidated through a combination of experimental and numerical simulation methods. The analysis of cleaning efficiency reveals that the surface-active nanoparticle composite solution is widely distributed throughout most microchannels in the model. The mechanism by which this solution induces wetting inversion to improve the flow efficiency is elaborated. This study systematically clarifies the mechanism of wetting reversal in nanofluids by combining experiments with numerical simulations, providing an important foundation for understanding the flow behavior of surface-active nanoparticle composite solutions at multiphase interfaces.