Recent studies have identified microneedle (MN) arrays as promising alternatives for transdermal drug delivery. This study investigated the properties of novel staggered MN arrays design featuring two distinct heights of MNs. The staggered MN arrays were precisely fabricated via PμSL light-cured 3D printing technology. The arrays were systematically evaluated for their morphology, fracture force, skin penetration ability, penetration mechanism, and drug delivery capability. The results demonstrated that the staggered MN arrays punctured the skin incrementally, leveraging the benefits of skin deformation during the puncture process. This approach effectively reduced the puncture force needed, achieving a maximum reduction of approximately 80.27% due to variations in the staggered height. Additionally, the staggered design facilitated skin penetration, as confirmed by the results of the rat skin hematoxylin-eosin (H&E) staining experiments. Compared with 3D-printed planar structures and highly uniform MN arrays, the staggered design exhibited enhanced hydrophilicity, as evidenced by a reduction in the contact angle from approximately 93° to 70°. Simulated drug release images of both coated and hollow staggered MNs illustrated the release and delivery capabilities of these structures across various skin layers, and the staggered design expanded the effective area of the MN arrays within the vertical dimension of the skin layers. This study offers both experimental and theoretical foundations for developing MN arrays with three-dimensional structural distributions, thereby facilitating advancements in MN array technology.
Keywords: 3D printing; microneedle; microneedle penetration; various heights.