Stereolithographic 3D Printing for Deterministic Control over Integration in Dual-Material Composites.

This work introduces a rapid and facile approach to predictably control integration between two materials with divergent properties. Programmed integration between photopolymerizable soft and stiff hydrogels was investigated for their promise in applications such as tissue engineering where heterogeneous properties are often desired. Spatial control afforded by grayscale 3D printing was leveraged to define regions at the interface that permit diffusive transport of a second material in-filled into the 3D printed part. The printing parameters (i.e., effective exposure dose) for the resin were correlated directly to mesh size to achieve controlled diffusion. Applying this information to grayscale exposures led to a range of distances over which integration was achieved with high fidelity. A prescribed finite distance of integration between soft and stiff hydrogels led to a 33% increase in strain to failure under tensile testing and eliminated failure at the interface. The feasibility of this approach was demonstrated in a layer-by-layer 3D printed part fabricated by stereolithography, which was subsequently infilled with a soft hydrogel containing osteoblastic cells. In summary, this approach holds promise for applications where integration of multiple materials and living cells is needed by allowing precise control over integration and reducing mechanical failure at contrasting material interfaces.