Multiple initiators and dyes for continuous Digital Light Processing (cDLP) additive manufacture of resorbable bone tissue engineering scaffolds: A new method and new material to fabricate resorbable scaffold for bone tissue engineering via continuous Digital Light Processing

The formulation of resorbable polymer resins for light-based additive manufacturing of tissue engineered scaffolds goes beyond resin chemistry. There are at least four parameters that allow the transition from individual layer curing to 3D printing; they are: layer thickness, overcuring, step size, and inter-layer binding. Overcuring is the thickness of the layer minus step size. Overcuring distance limits surface feature resolution in the between-layer direction. Strength is an indication of crosslinking density and a function of inter-layer binding or 'stitching'. 3D printed scaffolds must be sufficiently strong to endure cleaning of unpolymerised polymer from internal pore spaces without deforming. We report our study of the effect of exposure time on strength and layer thickness while holding step size constant. Increased overcuring dramatically increases scaffold strength. High resolution implants depend on sufficient energy from the light source and a well-tuned resin consisting of: polymer, initiator(s), and perhaps dye(s), solvent(s), and biologic(s).