Temperature dependence of interfacial properties and viscosity of nanofluids for droplet-based microfluidics

Interfacial tension and viscosity of a liquid play an important role in microfluidic systems. In this study, temperature dependence of surface tension, interfacial tension and viscosity of a nanofluid are investigated for its applicability in droplet-based microfluidics. Experimental results show that nanofluid having TiO2 nanoparticles of 15 nm diameters in deionized water exhibit substantially smaller surface tension and oil-based interfacial tension than those of the base fluid (i.e. deionized water). These surface and interfacial tensions of this nanofluid were found to decrease almost linearly with increasing temperature. The Brownian motion of nanoparticles in the base fluid was identified as a possible mechanism for reduced surface and interfacial tensions of the nanofluid. The measured effective viscosity of nanofluid was found to be insignificantly higher than that of base fluid and to decreases with increasing fluid temperature. The dependency on temperature of the droplet formation at T-junction of a microfluidic device is also studied and nanofluid shows larger droplet size compared to its base fluid.