Unconventional direct ink writing of polyelectrolyte films

This article focuses on fundamentally analyzing the morphology of polyelectrolyte-based layer-by-layer (LbL) films, created using an unconventional direct ink writing (u-DIW) approach that allows printing low-viscosity inks via capillary action. With two oppositely charged weak polyelectrolytes as inks and using a range of characterization techniques, we have compared the films developed using this new approach against traditional dip-coating in terms of their key morphological features. Our results suggest that the extent of polyelectrolyte interdiffusion within the films is limited in the case of the u-DIW approach causing the formation of thinner films versus dip-coating. In comparison to traditional dip-coating, u-DIW has the advantage of enabling the formation of homogenous films with equivalent properties, but with significantly lower material usage. The fundamental analyses presented in this article will likely facilitate the application of LbL in various fields ranging from separations to biomedical drug delivery.