Additive biofabrication of silicone scaffolds for tissue engineering: from mold casting to direct ink writing

Abstract Additive manufacturing has become an essential technique for fabricating bioscaffolds with well-controlled architectures, enabling systematic investigation of pore geometry and its influence on cellular behavior. Among the materials available, silicone-based scaffolds are particularly attractive for their biocompatibility and mechanical stability, while achieving accurate three-dimensional (3D) geometries remains challenging. This study presents the first comprehensive comparative investigation of silicone scaffold fabrication, systematically evaluating the geometric fidelity, structural integrity, and biocompatibility across three pore design ratios (length-to-width 1:1, 1:1.5, and 1:2) and two formats (two-dimensional single-layer and 3D double-layer scaffolds). Two fabrication routes were compared: (1) mold casting of polydimethylsiloxane (PDMS) using fused deposition modeling molds, and (2) direct ink writing (DIW) of room-temperature vulcanizing (RTV) silicone. For RTV scaffolds, both continuous printing and a segmented DIW strategy with periodic pauses were examined, the latter allowing partial curing of underlying layers to mitigate gravitational sagging and enhance vertical fidelity. Biocompatibility assays with P19 cells confirmed comparable proliferation among PDMS, RTV, and glass controls ( p = 0.183), with significant growth from day 3 to day 5 ( p < 0.001). Morphological analysis revealed method-dependent trade-offs: PDMS scaffolds benefited from mold support but exhibited surface burrs and undersized pores (up to 0.11 mm deviation), while RTV scaffolds achieved smoother edges and better lateral accuracy yet suffered from vertical collapse (∼0.09 mm height loss, 22.5% error). Incorporating segmented pauses effectively improved RTV scaffold uniformity, reducing maximum deviation to 0.04 mm and significantly enhancing pore width ( p = 4.22 × 10 − ₇ ) and height ( p = 0.000 173). This work establishes a systematic comparative framework and practical design guidelines for selecting and adapting silicone-based scaffold fabrication routes based on specific application requirements. Rather than identifying a single optimal strategy, findings here elucidate key manufacturing-dependent trade-offs, providing rational guidance for tailoring silicone scaffold architectures in future tissue engineering applications.