Flexible resins lattices produced by stereolithography for biomedical applications

Stereolithography offers a promising solution to produce bespoke structures as surgical guides, models, and implants. The high aspect ratio of the obtained samples combined with different and tailorable mechanical properties make this technique very suitable for 3D-printed medical solutions. However, the epoxy resins used for this technology are toxic and need to be cured and washed very carefully to be used in contact with biological tissues. Most of the time these materials are used for orthoses and external structures instead of implants or tissue engineering scaffolds. Nowadays, lattice structures are achieving specific attention due to the possibility of tailoring the mechanical properties with lightweight geometries that can be 3D printed with several materials. The drawback point is that all the biomedical resins are rigid and show a fragile, although with relatively high maximum stress values, behavior. Moreover, it is even more difficult to fabricate both a flexible and a transparent part, especially by lithography polymerization, and transparent materials are usually required for certain biomedical applications. In this paper, we wanted to obtain a lattice structure that can be suitable for silicon liners as part of knee external prostheses with a flexible biocompatible, and transparent resin.