The building blocks behind the Electrohydrodynamics of non-polar 2Dinks

TL;DR

This study characterizes the rheological behavior of 2D nanomaterial inks under electric fields, revealing how electric and nanoparticle properties influence filament stability in electrohydrodynamic processes.

Contribution

It provides a comprehensive rheological analysis of 2D-ink dispersions in electric fields, highlighting effects on filament thinning and stability relevant to EHD jet printing.

Findings

Electric fields induce vortices affecting filament stability.

Nanoparticle type influences conductivity and permittivity.

Electric fields have limited impact on shear viscosity.

Abstract

This work provides a complete rheological characterization of 2D-inks in electric fields with different intensities and orientations to the imposed flow field. 2D nanomaterials used in this study are graphene nanoplatelets, hexagonal boron-nitride, and molybdenum disulfide. These materials with different electric properties are dispersed in a non-polar solvent (Toluene) with different concentrations of Ethyl Cellulose (EC), providing Newtonian or viscoelastic characteristics. Shear rheology tests show that the presence of nanoparticles barely changes the fluid behavior from the carrier fluid, and the application of an electric field perpendicular to the flow does not result in electrorheological behavior. However, extensional experiments, which mimic the actual EHD jet printing conditions, allowed the observation of the influence of both the particles and the electric field aligned on the filament thinning process. It was observed that the electric field generates vortices due to an electrophoretic effect in the carrier fluid when EC is present in the formulations, which has severe consequences on the stability of the liquid bridges, whereas it scarcely affects the shear viscosity; additionally, the kind of 2D nanoparticles modifies also the conductivity and permittivity of the solution, inducing Maxwell stresses that also make the filament more stable against surface tension.