Phase behavior and rheological properties of polyelectrolyte inks for direct-write assembly.

Three-dimensional (3-D) structures with micron-sized features have been fabricated via the direct-write assembly of polyelectrolyte inks. By mixing oppositely charged species under solution conditions that promote polyelectrolyte exchange reactions, we have created concentrated fluids capable of flowing through microscale deposition nozzles. Ink deposition into an alcohol/water coagulation reservoir yielded polyelectrolyte filaments that rapidly solidify to enable three-dimensional patterning of microperiodic structures with self-supporting features. The influence of ink and reservoir chemistry on the phase behavior, rheological properties, and assembly of concentrated polyelectrolyte complexes is reported with an emphasis on the optimal conditions for 3-D writing.