Effect of monodisperse nanoparticle size on flow fluency of inkjet printing

Abstract

To investigate the influence of nanofluid emulsion particle size on flow smoothness, 5 % (w/w) latex particle dispersions and 1 % (w/w) inks were prepared from monodisperse polystyrene (PSt) and poly(sodium styrene sulfonate-co-styrene) (P(SS-co-St)) latex particles. The filtration rate of the dispersions was tested by vacuum filtration, and the coefficient of friction (COF) was measured for mathematical model analysis of the force conditions on latex particles in the dispersions. The inkjet process of the ink was observed, followed by density functional theory (DFT) calculations to determine the interaction forces between the components of the ink. The results showed that when the filter pore size was 1 μm, the one-time maximum circulation of the dispersion decreased with increasing particle size. When the filter pore sizes were 5 and 10 μm, the PSt system exhibited a phenomenon where the one-time maximum circulation first decreased and then slightly increased with increasing particle size, while P(SS-co-St) maintained its original trend. Furthermore, with increasing particle size dispersity, the one-time maximum circulation of the dispersion under 5 and 10 μm filters showed a significant increase. Under the same dynamic viscosity and surface tension, monodisperse PSt ink could not be jetted beyond a size of 82 nm, but the two inks with greater dispersity after compounding could still be ejected. The inkjet threshold for monodisperse P(SS-co-St) ink exceeded 201 nm, while the compounded latex particle inks could be successfully ejected. DFT calculations show that the charge on the surface of P(SS-co-St) latex particles can maintain particle stability during flows, while the surfactant on the PSt surface is easily desorbed, thus impeding the flow. This study provides a new method for studying the flow resistance of nanofluids in microporous channels and further improves the theoretical basis of nanofluids in inkjet printing.