Shape-controlled microneedles for transdermal drug delivery by direct-material-extrusion 3D printing

Fused deposition modelling (FDM) is a cost-effective and widely accessible additive manufacturing technology; however, its limitations in precision and surface finish hinder its suitability for fabricating microneedles (MNs), particularly for medical applications. This study introduces a novel platform that integrates the principles of drawing lithography with FDM, enabling precise and flexible shape control of extruded filaments. By regulating the non-Newtonian fluid deformation process and the thermodynamics of molten filaments, we successfully fabricate high-quality MN devices with diverse functionalities. This approach achieves needle tip sizes as small as ∼25 µm and variable needle lengths ranging from approximately 600 to 2400 µm by modulating filament drawing speed and distance, facilitating effective skin penetration at varying depths of the stratum corneum. Furthermore, we demonstrate the fabrication of MNs with distinct functionalities, including rapidly separable, bionic serrated, and multilayered designs, supported by mechanical verification and skin penetration assessments. This study innovates the conventional layer-by-layer manufacturing paradigm of FDM, establishing an efficient workflow for high-precision, customisable MN fabrication and broadening the applicability of FDM for biomedical engineering.