(152bl) Unconventional Direct Ink-Writing for Polyelectrolyte Multilayer Films

My talk will describe a surface-force driven unconventional direct ink writing technique for the fabrication of polyelectrolyte multilayer membranes. Layer-by-layer (LBL) assembly involves the deposition of two oppositely charged polyelectrolytes on a particular substrate. Self-assembled polyelectrolyte multilayer (PEM) films enable a range of versatile properties like porosity, thickness, surface charge, roughness, etc. and have diverse applications in various fields such as drug delivery, and membrane modifications. The conventional method of fabrication, i.e., dip-coating, requires a large amount of solution for fabricating PEM films and is difficult to scale up. To address the scalability issue, this study aims to fabricate polyelectrolyte multilayer films using an unconventional direct ink writing (u-DIW) technique. In this method, polyelectrolyte films can be printed on a substrate using capillary forces, without the application of external pressure during printing. In this work, two alternatively charged polyelectrolytes were used – poly (allyl amine hydrochloride) (PAH) (+) with –NH₂ functional group and poly (acrylic acid) (PAA) (–) with –COOH functional group. PEM films were created by altering various polyelectrolyte parameters such as molecular weight, deposition time, pH change, etc. In addition to non-porous PEM films, porous polyelectrolyte films were also fabricated by the utilization of simple post acidic treatment steps. When comparing the critical characteristics of resulting u-DIW films against traditional dip-coated films, it was found that the two fabrication techniques were largely interchangeable and exhibiting similar morphological properties in terms of porosity, thickness, contact angle, roughness, etc. Our preliminary experiments also show that the PEM membranes created using u-DIW have identical water permeance and salt rejection characteristics to those fabricated with dip-coating technique, while requiring ~10X less solvent (water) usage. The findings from this study indicate that PEM membranes with comparable morphological properties can be created using this new u-DIW approach, effectively enabling the widespread application of u-DIW enabled LBL.