Drop-on-demand assessment of microdrops of dilute ZnO–water nanofluids

Abstract

Shrinking device dimensions demand a high level of control and manipulation of materials at microscale and nanoscale. Microfluidics has a diverse application spectrum including thermal management of chips, point-of-care diagnostics, and biomedical analysis, to name a few. Inkjet printing (IJP) is a manufacturing method used for micro-/nanofabrication and surface restructuring, and liquid inks are characterized based on their density, surface tension, and viscosity for their printability. Nanofluids as colloidal dispersions of nanoparticles hold potential in various heating, cooling, lubricating, and biomedical applications with the premise of nanoparticles’ size and concentration effects and interactions between nanoparticle–nanoparticle and nanoparticle–base fluid. In order to explore the microfluidic behavior of nanofluids, using micro-volumes of nanofluids and/or confining them in a micro-system is essential. With this motivation, we present a printability assessment on the potential of low concentration ZnO–water nanofluids by utilizing a combined theoretical and experimental approach. For 0.05 vol. %–0.4 vol. % of ZnO–water nanofluids, results showed that for a nozzle diameter of 25 μm, the samples do not exhibit the energy necessary for drop formation, while for 50 μm and 100 μm nozzle diameters, the samples behave as satellite droplets. Although satellite droplets were generally not desirable for IJP, the recently introduced satellite droplet printing concept may be applicable to the printing of aqueous nano-ZnO dispersions considered in this work.