3D Printing of Silicone Organogel Elastomers for Structured Soft Biomaterials.

Creating customizable soft medical implants and devices tailored to patient-specific anatomy represents a significant challenge in healthcare, requiring 3D-printable materials with viscoelastic properties similar to those of natural tissue, high adaptability, and biocompatibility. Here, we develop a family of silicone organogel inks for 3D printing of tunable soft biomaterials via direct ink writing (DIW). We have developed a set of ink formulations comprising photo-cross-linkable silicone polymers, silicone oil, and fumed silica nanoparticles to modify the rheological behavior of the inks, optimize their printability, and control the viscoelastic properties of the printed organogel materials. The formulation approach decouples ink viscosity and shear-thinning behavior from the properties of the printed organogel materials, yielding soft elastomeric materials spanning 3 orders of magnitude in moduli. These organogel inks were used in multimaterial DIW to print soft-structured materials with nonlinear behavior, leveraging graded spatial heterogeneity to introduce stress dissipation and out-of-plane deformation mechanisms. The biocompatibility of these organogel materials was analyzed through a variety of cytotoxicity assays with human dermal fibroblasts, showing no significant toxicity, even in formulations with high silicone oil content. Due to their wide tunability, biocompatibility, and easy printability, these silicone organogel materials show great potential for 3D printing customizable soft devices useful in many applications, including patient-specific implants, prosthetics, wearable devices, medical phantoms, soft robotics, and medical devices.