Evaluation of 3D Printability and Biocompatibility of Microfluidic Resin for Fabrication of Solid Microneedles.

In this study, we have employed Digital Light Processing (DLP) printing technology for the fabrication of solid microneedle (MN) arrays. Several arrays with various geometries, such as cones, three-sided pyramids and four-sided pyramids, with different height to aspect ratios of 1:1, 2:1 and 3:1, were printed. Post-processing curing optimizations showed that optimal mechanical properties of the photocurable resin were obtained at 40 °C and 60 min. Ex vivo skin studies showed that piercing forces, penetration depth and penetration width were affected by the MN geometry and height to aspect ratio. Cone-shaped MNs required lower applied forces to penetrate skin and showed higher penetration depth with increasing height to aspect ratio, followed by three-sided and four-sided printed arrays. Cytotoxicity studies presented 84% cell viability of human fibroblasts after 2.5 h, suggesting the very good biocompatibility of the photocurable resin. Overall, DLP demonstrated excellent printing capacity and high resolution for a variety of MN designs.