3D printing of salt-like granular polyacrylamide as sacrificial molds for shaping versatile materials

Digital light processing 3D printing is a powerful manufacturing technology for shaping materials into complex geometries with high resolution. However, the rheological and chemical requirements for printing limit the use of materials to photoactive resins. Here, we propose a versatile manufacturing platform for constructing versatile materials using DLP-printed water-soluble granular polyacrylamide as sacrificial molds. The polymerization-induced phase separation during printing results in a close packed granular geometry with intrinsic micropores, which greatly accelerates the dissolution rate of polyacrylamide. Combined with precise control over the molecular weight, this salt-like sacrificial mold can be fully dissolved in neutral water at room temperature within 30 min. Furthermore, significant surface oxygen inhibition promotes the leveling and spreading of liquid resin on the cured part surfaces, achieving a printing speed of 375 mm/h in a top-down printer. Due to the mild conditions for mold removal, complex-shaped architectures can be created from a variety of compositions, including temperature-sensitive low-melting alloys, alkaline-degradable polyesters, as well as widely used materials such as silicone rubber, polyurethane, polyolefin elastomer, and epoxy. Considering the fast mold dissolution rate and mild dissolution conditions, the present platform represents a potential low-cost, and universal indirect 3D printing method for shaping versatile materials.