Architecting nanoconfined multiphase gels as a reprocessable and multistimuli-responsive 4D printing platform

4D printed shape memory gels (SMGs) have shown great potential for bionic scaffolds and soft robotics. However, their practical deployment is often limited by insufficient mechanical strength and reprocessability. Here, a nanoconfined multiphase gel strategy to develop reprocessable and multistimuli-responsive 4D-printed SMGs is proposed. The developed poly(vinyl alcohol)/chitin nanocrystals/paraffin multiphase gel (PCPG) employs zwitterionic chitin nanocrystals (ChNC) as an interfacial stabilizer to construct a nanoconfined environment, mediated by abundant interfacial interactions—hydrophobic with the paraffin (PW) microphase and hydrogen bonding with the poly(vinyl alcohol) (PVA) gel matrix. These synergistic interactions lead to a remarkable enhancement in tensile strength (by ≈ 50%, up to ~ 1 MPa). A high loading of phase-change PW (volume fraction >70%) imparts outstanding shape memory properties and printability, with fixation and recovery ratios both exceeding 95%, along with high responsiveness to both thermal and acoustic stimuli. Importantly, the dynamically crosslinked network combined with efficient nanoconfinement enables excellent reprocessability, the 4D-printed PCPG retains over 85% of its original mechanical and shape memory performance after ten reprocessing cycles. This strategy successfully merges nanoconfinement design with reprocessability, providing a sustainable platform for high-performance 4D-printed bionic scaffolds.