High-resolution 3D printing of modified pullulan elastic hydrogels via solvent-induced shrinkage.

3D-printable hydrogels confront two core bottlenecks: the trade-off among high printing resolution, fabrication efficiency, and structural fidelity, as well as the inherently poor mechanical performance of conventional hydrogel materials. Herein, we fabricated a dual-network photo-crosslinkable pullulan-based hydrogel system, in which the mass ratio of Pul-MA to uHMW Pul-NB and solid content jointly govern the printability and mechanical behaviors of hydrogel inks. A simple ethanol post-treatment induces relatively homogeneous volumetric shrinkage within printed architectures. Specifically, treatment with 75% (v/v) ethanol shrinks the diameter of hydrogel micro-filaments down to 51.84 ± 0.4% of the original dimension, which greatly improves the feature resolution of printed structures. The ethanol-triggered shrinkage exhibits favourable partial reversibility, which holds promise for programmable dimensional regulation through further optimization of post-treatment cycles, accompanied by simultaneous mechanical reinforcement of hydrogel scaffolds. Complex architectures including bionic auricular models and co-axially printed tubular scaffolds were successfully fabricated to verify the practicability of this strategy. This solvent-induced shrinkage-assisted resolution-enhancing method serves as a hardware-free post-processing strategy for high-precision additive manufacturing of biomaterials, and holds practical value for research fields including tissue engineering, soft robotics and microfluidic devices.