Design and fabrication of a 3D stereolithography-printable hydrophilic silicone-based elastic composite biomimetic hydrogel

Additive manufacturing of silicone-based, tissue-mimetic hydrogels is challenging because conventional silicones are hydrophobic, highly viscous, and slow-curing—properties that are incompatible with high-resolution stereolithography (SLA). This study developed a new hydrophilic silicone-based elastic composite hydrogel with low pre-gel viscosity and rapid photocuring designed specifically for SLA printing. The authors first methacrylated a polar aminosilicone to create a photocurable silicone network (SilMA) but observed a relatively low degree of substitution (~35%), which limited crosslinking density and slowed curing. To enable SLA printability without printer modification, they introduced a second polymer network by adding acrylamide (AA) and PEGDMA crosslinker to form an interpenetrating network (IPN) upon UV exposure. Increasing AA content improved transparency at the 405 nm printer wavelength (improving curing depth) and reduced viscosity; formulations with higher AA achieved favorable flowability for standard SLA layer renewal. Using an Anycubic Photon Mono 4K SLA printer, optimized exposure parameters (2 s per layer) produced high-quality prints with ~100 µm X/Y/Z resolution and enabled printing of biomimetic geometries (scaled cartilage-on-bone and an elastic artery model). The resulting hydrogel was hydrophilic (contact angles ~55–60°) and showed high water uptake that increased with AA content (equilibrium swelling reaching ~104–112% in water at 22–37°C and ~121% in body-fluid mimics). Mechanical characterization showed AA content tuned compressive modulus into the range of articular cartilage zones: ~0.28 ± 0.04 MPa (0.5 part AA) to ~0.72 ± 0.05 MPa (0.8 part AA) at 10% compression, with low damping (elastic-dominant rheology) and excellent recovery over 10 cyclic compression cycles with near-zero permanent set. Cytocompatibility testing with human corneal epithelial cells showed no overt cytotoxicity over 6 days. Overall, the work introduces an SLA-printable hydrophilic silicone–hydrogel composite that integrates cartilage-like compressive mechanics, elasticity, and print resolution for biomimetic soft-tissue structures.