A high-precision method for manufacturing tunable solid microneedles using dicing saw and xenon difluoride-induced dry etching

Abstract

Numerous fabrication techniques have been employed to produce solid microneedles (MNs); yet precise manufacturing of MNs with adjustable features (height, aspect ratio, and array number) remains the main limitation. Developing tunable MNs holds immense promise for personalized and efficient drug delivery systems. In this study, we utilized a combination of dicing saw and XeF2 isotropic dry etching processes to fabricate solid MNs with tunable characteristics. We herein created rectangular arrays using a dicing saw with desired geometry followed by dry etching to form MN arrays without further processing. Employing optimized parameters, the average heights of the MNs were 522 ± 15 µm, 614 ± 42 µm, and 698 ± 22 µm for initial pattern depths of 500 µm, 600 µm, and 700 µm, respectively. Moreover, we achieved an aspect ratio as high as 3.7, a radius of curvature less than 10 µm, and a tip angle as low as 6.4o. The mechanical and surface properties of the MNs were enhanced through magnetron sputtering with titanium. An ex vivo penetration test conducted on porcine skin demonstrated the significant potential of these MNs for transdermal drug delivery in future investigations. Overall, a cost-effective production of a single solid MN patch, featuring 400 MN arrays per cm2, can be achieved within a remarkably short timeframe (approximately 2 h). Investigating fundamental principles, this study addresses the persistent challenge in manufacturing solid MNs with adjustable features, such as height, aspect ratio, and array number. This presents a substantial advantage over alternative fabrication techniques.