Precipitation printing towards diverse materials, mechanical tailoring and functional devices

Additive manufacturing allows for the fabrication of complex structures which are hard to achieve through conventional machining, extrusion, injection molding or blow molding processes. Current additive manufacturing methods for polymers, such as vat photopolymerization, powder bed fusion, material extrusion and binder jetting, still have limitations on the types of polymers that can be 3D printed. Recently, a novel solution-based polymer additive manufacturing method, termed precipitation printing, is developed which is based on the solubility of the polymer being printed in two mutually miscible solvents. In this work, the precipitation printing technique is further developed to expand the range of applicable materials, towards different thermoplastics (poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA)), thermoset rubber (acrylonitrile butadiene rubber (NBR)) and polymer nanocomposites (multiwalled carbon nanotubes (MWCNTs)-PVDF). The printing process is rapid and enables the realization of large structures with complex geometries as well as printing at a higher resolution than the material extrusion method, while also allowing the fabrication of micro-scale structures with greater than 100 μm resolution. Porosity and mechanical property tailoring of the precipitation printed materials are achievable through the control of process parameters, such as solvent/non-solvent pair selection, salinity of the non-solvent and printing temperature. In addition, the successful demonstrations of a directly 3D printed NBR check valve and a MWCNTs-PVDF strain gauge indicate the great potential for precipitation printing as a promising one-step process for the production of functional devices.