Solvent-Rich Pre-Coagulation Bath for Tunable Liquid-State Fusion Enables Robust Two-Step Polymer Embedded Printing.

Effective interlayer fusion is a critical step enabling a 3D printing process. For engineering polymer printing, interlayer fusion is usually either heat-enabled or binder-based, which may introduce thermal residual stress, warpage, and undesirable impurities. To overcome such challenges, a two-step immersion phase separation (IPS)-based room-temperature polymer fusion and solidification approach for self-supported engineering polymer printing, termed IPS-embedded 3D printing (IPS-E3DP) is introduced. IPS-E3DP is implemented by first depositing polymer inks in a solvent-rich yield-stress pre-coagulation support bath to have an intermediate green part and then immersing the intermediate green part in a non-solvent coagulation bath for complete solidification. During the first critical step, dissolved polymer ink holds its deposited shape and fuses with a previously deposited polymeric feature in the pre-coagulation support bath. Specifically, it is the high-concentration solvent bath (usually 80% or higher) that enables tunable liquid-state fusion of polymers when the deposited polymer solidifies, and it is the yield-stress support bath that prevents the deposited polymer ink from spreading and deformation during fusion. IPS-E3DP enables the self-supported room-temperature high-fidelity printing of a wide range of engineering polymers, blends, and composites with superior geometric complexity. The process can be tailored as a polymer binder-based printing approach for versatile material printing.