Geometrically adaptive porous shape memory polymers towards personalized biomedical devices

Porous shape memory polymers (SMPs) can execute large volume expansion from their compressed temporary shapes to porous permanent shapes, which present promising practical potentials in biomedical and aerospace fields. While constructing sophisticated geometries are essential for achieving the corresponding functions of the foams, the original shapes which are typically determined by molds cannot be post-tuned in a customized fashion. Here we propose an easy but effective emulsion lyophilization method to fabricate porous SMPs, the original shapes of which can be post-regulated via a two-stage curing mechanism. A thermo-curable acrylate emulsion and a photo-curable polyurethane emulsion were prepared individually and then mixed in proportion. After lyophilization of the mixed emulsion, porous SMPs were prepared due to the first thermo-curing stage between epoxy and amine groups from the acrylate emulsion. The foams can be temporarily programmed into alternative shapes with relatively complex geometries which can afterwards be permanently fixed through the secondary photo-curing stage. In this way, simple permanent shapes of the porous SMPs determined by planar molds were converted into customized three-dimensional ones taking advantage of various deformation such as bending, imprinting, and twisting. Accordingly, customized biomedical devices were fabricated via the two-stage curing process, inspiring further application opportunities for porous SMPs.