Capillary breakup of molybdenum disulfide particle-laden viscoelastic fluids

The exceptional mechanical, electrical, and optical properties of two-dimensional (2D) particles, such as molybdenum disulfide (MoS2), have driven their incorporation into functional inks for advanced printing techniques. In many of these processes, extensional deformation governs the separation of ink from the feeding system to the substrate, with capillary breakup significantly influencing print quality and resolution. This study investigates the filament thinning dynamics of MoS2 suspensions under varying electric fields aligned with the flow direction. The results reveal that increasing particle concentration accelerates the thinning rate in the inertio-capillary regime, leading to a shorter filament lifetime. Furthermore, the critical Ohnesorge number defining the transition between inertio-capillary and visco-capillary regimes is shown to depend on the particle concentration and electric field strength. Interestingly, the apparent extensional relaxation time decreases with increasing particle concentration, disappearing entirely at 0.50% and 0.75% w/w, before reemerging at higher concentrations in the absence of an electric field. These findings provide new insights into the complex interplay of particle concentration, electric fields, and extensional flow, with implications for optimizing 2D particle-laden inks in printing applications.