Transportation of Janus nanoparticles in confined nanochannels: a molecular dynamics simulation†
Janus nanoparticles (JNPs) have drawn significant attention due to their unique surface with dual character. In this study, the transportation of two-phase fluids with JNPs in an ultra-confined channel was studied by molecular dynamics (MD) simulations. The results indicated that the fluid displacement was hindered by JNPs, which was, to an extent, significantly dependent on the concentration of the NPs self-assembled at the fluid interface; compared to the case of NPs with uniform surface properties, the determining migration states for JNPs that influenced the displacement process were self-assembled at the fluid interface and aggregated in the three-phase contact region; this modified the interfacial tension and the three-phase contact angle. These key migration states were validated by the potential of the mean force of JNPs transporting from water to the oil phase. The capillary pressure calculated by the local pressure distribution was found to be the key factor driving the displacement process of the nanofluids with JNPs. Our findings reveal the microscopic transportation mechanism for fluids with JNPs into porous materials, which have significant implication for the application of JNPs in the fields such as enhanced oil recovery, drug delivery, and inkjet printing.