4D-Printing biocompatible polymer with high mechanical performance for clear aligners

Clear aligners have become a preferred orthodontic solution due to their aesthetics, comfort, and convenience. However, current aligners still suffer from poor fit caused by thermoforming-induced dimensional inaccuracies and force mismatch due to stress relaxation in thermoplastic materials. Here we address these limitations by developing a biocompatible, highly transparent polyurethane-based material (PUP) tailored for high-precision DLP printing. The PUP ink enables rapid, spatially resolved curing within 30 s and supports high-fidelity printing with feature sizes down to ~10 μm. Moreover, 4D-printed PUP aligners combine accurate fit with programmable, long-term force delivery and can be reshaped for multiple treatment stages. Notably, the representative formulation meets clear-aligner-relevant yield thresholds (yield strength > 25 MPa and yield strain > 4%), supporting stable elastic force output within a clinically meaningful deformation window. This work demonstrates a smart aligner strategy that integrates precision manufacturing with active force control through shape memory, offering a practical route toward next-generation personalized orthodontic devices.