J.P. Killgore
National Institute of Standards and Technology,
United States
Keywords: 3D printing, bioprinting, additive manufacturing, biomaterials
Summary:
Vat photopolymerization, a high-resolution, high-throughput 3D-printing method has yielded major breakthroughs in complexity and scale of printed parts. By combining vat photopolymerization with hydrogel bioinks, numerous new opportunities for drug delivery, organ-on-a-chip, tissue scaffold and even artificial organs have emerged. For both processing and application of hydrogels, the mechanics and chemistry of the gel are critical considerations that must be optimized. If a gel is too weak, the forces induced by printing will cause print-failure. However, the printing process relies on absorption of light in the bio-ink, which introduces a gradient in mechanical properties in every layer, typically weakest at layer-layer interfaces. Mechanical properties must also be considered in biological applications of hydrogels wherein the mechanosensitivity of cells can results in very different cellular growth depending on surface properties. In an effort to understand the tunability of gel mechanical properties, we have characterized gels by atomic force microscopy and nanoindentation in fully printed parts and on single printed layers. Furthermore, we have conducted investigations both ex-situ and in-situ to the printing process. We establish the first quantitative measurements of modulus at the gel-front, where the layer transitions from solid back to liquid monomer.