Particle Loading Effects on Additively Manufactured and Laser Cured Medical Grade Silicone

A proposed benefit to additive manufacturing (AM) silicone components is the ability to selectively add fillers such as agents to make drug delivery devices. Laser curing silicones have benefits such as selective or graded curing of specific locations in the part. A challenge with high-temperature extrusion-based AM processes is understanding how particles of various thermal sensitivities, sizes, and loading amounts may affect the AM build parameters, polymer crosslink densities, and final products produced. This article investigates the effect of particle loading on laser-cured medical-grade silicone. Die swelling of silica gel-loaded silicone, chosen as a relatively nonthermally sensitive representative filler for drug agents, was evaluated as a function of extrusion speed, particle size, and particle loading amount. A design of experiments (DoE) on silica gel-loaded samples through tetrahydrofuran (THF) swell studies was done to explore how layer height, particle size, and particle loading amount may affect crosslink density. Last, the AM process with the female hormone 2-methoxyestradiol (2-Me2) and the drug Cyclosporin was investigated using nuclear magnetic resonance (NMR) spectroscopy and high-performance liquid chromatography (HPLC) elution to observe potential alterations of the final product. The results show promise for drug-loaded silicone samples fabricated using an extrude and laser curing AM technique.