3D-Printed Microinjection Needle Arrays via a Hybrid DLP-Direct Laser Writing Strategy

Microinjection protocols are ubiquitous throughout biomedical fields, with hollow microneedle arrays (MNAs) offering distinctive benefits in both research and clinical settings. Unfortunately, manufacturing-associated barriers remain a critical impediment to emerging applications that demand high-density arrays of hollow, high-aspect-ratio microneedles. To address such challenges, here, a hybrid additive manufacturing approach that combines digital light processing (DLP) 3D printing with ex situ direct laser writing (esDLW) is presented to enable new classes of MNAs for fluidic microinjections. Experimental results for esDLW-based 3D printing of arrays of high-aspect-ratio microneedles-with 30 mu m inner diameters, 50 mu m outer diameters, and 550 mu m heights, and arrayed with 100 mu m needle-to-needle spacing-directly onto DLP-printed capillaries reveal uncompromised fluidic integrity at the MNA-capillary interface during microfluidic cyclic burst-pressure testing for input pressures in excess of 250 kPa (n = 100 cycles). Ex vivo experiments perform using excised mouse brains reveal that the MNAs not only physically withstand penetration into and retraction from brain tissue but also yield effective and distributed microinjection of surrogate fluids and nanoparticle suspensions directly into the brains. In combination, the results suggest that the presented strategy for fabricating high-aspect-ratio, high-density, hollow MNAs could hold unique promise for biomedical microinjection applications.

Automated summary

This article presents a hybrid additive manufacturing approach combining digital light processing (DLP) 3D printing with ex situ direct laser writing (esDLW) to fabricate new types of microneedle arrays (MNAs) for fluidic microinjections. Experimental results show that the method can create high-density, high-aspect-ratio microneedle arrays with uncompromised fluidic integrity. Ex vivo experiments on mouse brains demonstrate that the MNAs can penetrate and retract from brain tissue and effectively perform microinjections. Overall, this fabrication strategy shows great promise for biomedical microinjection applications.