ADVANCING DIRECT LASER WRITING-BASED MICRONEEDLE ARRAYS

Abstract

Microneedle arrays (MNAs) are an emerging platform for minimally invasive drug delivery applications. This thesis investigates two key limitations in current 3D-printed hollow MNAs fabricated via direct laser writing (DLW): (1) inadequate mechanical performance of polymer-based MNAs for penetration into stiffer biological tissues, and (2) increased risk of collateral damage in sensitive environments due to uniformly distributed array geometries. To address the first challenge, polyhedral oligomeric silsesquioxane (POSS)-based fused silica glass MNAs were fabricated and evaluated. Experimental penetration testing in surrogate biomaterial demonstrated that glass MNAs reliably penetrate and are retrieved intact, while polymer MNAs fail structurally. These results highlight the enhanced mechanical properties of glass and its potential for applications in rigid tissues such as cartilage and tendon. To address the second challenge, a novel design framework termed strategic microneedle arrays (SMNAs) was introduced. SMNAs omit or reposition needles based on the spatial layout of critical features (e.g., vasculature) to reduce insertion-related trauma. Proof-of-concept testing with agarose blood vessel phantoms revealed that SMNAs preserved vessel integrity while conventional MNAs induced simulated rupture and leakage. Together, these contributions demonstrate how advances in material selection and design customization can improve microneedle performance, safety, and applicability across a broader range of biological environments.