One route to making flat panel color displays is by ink-jet printing of light emitting polymer solutions into pixel wells. Small differences in fluid elasticity or extensional viscosity impact the ability to make uniform micro-drops and consequently the commercial viability of this technology. Conventional techniques used for polymer melts (like oscillatory and normal stress measurements) cannot be used to quantify these effects for the polymer solutions employed in view of the small magnitudes involved.

A novel extensional rheometer developed at W.Virginia University was used to characterize the stretching behavior of various low viscosity model solutions (comparable to water) through the Trouton viscosity. The jetting behavior of these systems was determined using a custom-designed drop-on-demand apparatus and a camera. Key aspects of the process - tailing, ease-of-separation and satellite drop formation - were related to the extensional viscosity and enabled definition of the optimal processing window. The observed behavior was shown to be consistent with a simple mechanistic explanation in terms of a balance between the ease of drop formation and suppression of the Rayleigh instability phenomenon. This work – believed to be the first of its kind - provides a basis for efficient commercialization of this technology and future theoretical analysis.