Origami-Inspired Shape-Memory Stents Fabricated via Volumetric 3D-Printing

Introduction. Shape-memory stents capable of auto-expansion represent a promising strategy toward minimally invasive procedures. Inspired by origami folding principles [1], such devices can achieve compact deployment configurations and controlled expansion via exposure to body temperature by exploiting temperature-responsive shape memory polymers as stent material. This study explores the fabrication of shape-memory stents using volumetric 3D printing, a tomographic method capable of producing complex geometries within seconds and feature sizes down to 100 μm, depending on the resin formulation [2]. To achieve thermoresponsive behavior, we employed a functionalized poly(ε-caprolactone) (PCL), which was photo-crosslinked via thiol-ene chemistry [3], and incorporated principles of radical inhibition to improve print fidelity and control over polymerization [4]. Materials and Methods. A three-arm PCL (Mn = 8000 g·mol-1) [3] functionalized with alkene end-groups (3.44 x 10-4 mol·g-1, 91% substitution) was crosslinked via thiol-ene chemistry using pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) (Fig. 1c). The resin was photo-formulated with diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) as a photoinitiator and 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) as a radical inhibitor. Volumetric 3D-printing (Fig. 1b) was used to fabricate stent geometries with origami-inspired designs (Fig. 1a), followed by post-curing under UV light to ensure complete crosslinking. Material properties and shape-memory performance were evaluated via differential scanning calorimetry (DSC), rheological characterization, and thermo-mechanical actuation tests. Results. The stents (Fig. 2b) exhibited a shrinkage ratio of 38% and a melting temperature (Tm) of 44.7 °C, enabling temperature-triggered recovery from a temporary folded state to a predefined permanent shape. The photo-crosslinked network (Fig. 2c) demonstrated sufficient mechanical stability and shape fixity below Tm. The use of folding geometries with varying wall thicknesses enabled reproducible unfolding behavior during activation. Discussion. This work demonstrates that volumetric 3D-printing into functional PCL 3D constructs [3] can enable rapid fabrication of deployable biomedical devices with shape-memory properties. The auto-unfolding performance and processing precision achieved herein highlight the potential of this method for advanced medical device manufacturing, where minimally invasive delivery and geometry control are critical. Conclusions. An origami-inspired stent with shape-memory behavior was successfully fabricated via volumetric 3D-printing. The strategy combines material formulation, printing precision, and design strategy (Fig. 2a) to enable thermo-responsive shape recovery suitable for soft tissue applications. This approach paves the way towards customizable, auto-deployable implants. Future work will focus on tailoring the polymer network architecture by reducing the PCL molar mass or incorporating acrylate co-monomers to lower the Tm and enable activation at body temperature.