Low-cost fabrication of digital light processing 3D printed conical microneedles for biomedical applications

• Ultra-low cost DLP printers can be used to create functional microneedle molds. • Parametric input studies can be used to optimise microneedle geometry. • DLP printing layer height changes microneedle surface roughness and drug-coating capacity. • DLP printed microneedles can successfully penetrate skin for drug delivery applications. The 3D printing of microneedles has become an emerging area of research focus due to its ability to rapidly create microneedle arrays with parametrically variable geometry and composition. Through direct fabrication or via replica molding, 3D printed microneedles can facilitate iterative array assessment and act as a screening tool to quickly establish optimal parameters for tissue insertion and capacity for biomarker monitoring or drug release. However, the widespread adoption of 3D printing by microneedle array researcher group faces multiple barriers: (1) Investment in 3D printing systems that are traditionally associated with high-resolution pose a significant financial cost, (2) Current high-resolution printing methods are often slow and not conducive to rapid manufacturing, (3) Material selection can be limited in some ‘proprietary’ 3D printing systems (e.g. CLIP, SLA, or 2PP), (4) Given the multidisciplinary nature of the microneedle-field, researchers may not have the expertise to optimize printing parameters for a given material or printer. This work explores how ultra-low-cost digital light processing (DLP) printers can rapidly produce functional microneedle arrays for a variety of purposes, whether direct print, master mold production, or creation of coated microneedles, at a fraction of the cost of currently used systems. Further, this work highlights that high quality microneedle arrays can be created using DLP printing methods with reliability exceeding 98 %, tip radii on the order of 30 µm, and with appropriate parameter input optimization, high quality microneedle arrays can be fabricated that express desirable characteristics for multiple forms of solid microneedle array production.