Rapid water-triggered hardening of ethanol-softened shape memory polyurethane for shape fixation and minimally invasive biomedical applications

This study presents a rapid water-triggered hardening strategy for ethanol-softened shape memory polyurethanes (SMPU), including thermoset foams and thermoplastic polyurethane (TPU) films/membranes. The SMPU foam, once softened by 70 % ethanol, becomes highly compressible for minimally invasive delivery. Subsequent immersion in water effectively removes ethanol and restores mechanical stiffness of the foam within minutes, with the Young’s modulus increasing from 0.001 MPa (softened state) to over 0.8 MPa after 5 min—far surpassing air drying alone. This ethanol–water exchange mechanism enables shape fixation without the need for thermal activation or toxic solvents. The concept is further validated in TPU films and electrospun membranes, which exhibit localized and programmable shape recovery under similar treatment. In vascular phantom models, the SMPU foam demonstrates conformal filling of aneurysmal geometries with secure fixation post-hardening. These findings suggest a solvent-responsive, biocompatible platform suitable for embolization and other minimally invasive biomedical applications, offering a safer and faster alternative to traditional shape memory approaches.