Recently, heat-assisted vat photopolymerization received increasing attention because it can improve the mechanical properties of 3D printed products and permit the 3D printing of highly viscous biodegradable photopolymers. Even shape-memory thermoplastic photopolymers that are solid at room temperature have been successfully 3D printed by this technique. To address the challenges in PEG hydrogel printing, we propose here direct heat-assisted SLA/DLP printing of hydrophilic photopolymers that are not printable at room temperature (e.g., high MW PEG), and the subsequent transformation into hydrogels by simple post-printing swelling. We report the high-resolution fabrication of structurally complex, tough PEG hydrogels, using either a commercial bisacylphosphine oxide (BAPO) photoinitiator or a newly developed PEG-based macrophotoinitiator (BAPO-PEG). The manufacturing of the hydrogel objects consists of two steps: i) direct DLP printing of PEG (macro)monomers in the absence of water and ii) post-printing swelling of the 3D printed objects in water (Figure ). By tuning PEG chain length and resin composition, shape-memory PEG networks and corresponding hydrogels with complex geometries, excellent shape fidelity, and tunable mechanical strength can be produced. Finally, using a dual-macromonomer formulation in the presence of star shape BAPO-PEG, the "all-PEG" resin can be 3D printed into bioactive bone-mimicking hydrogel scaffolds without including organic solvents or water in the resin.