Scalable fabrication of microneedle arrays via spatially controlled UV exposure.

Hidetoshi Takahashi,Isao Shimoyama,Kiyoshi Matsumoto,Tesuo Kan,Yun Jung Heo,Nobuchika Arakawa,Ryuji Kawano

doi:10.1038/micronano.2016.49

Abstract

This paper describes a theoretical estimation of the geometry of negative epoxy-resist microneedles prepared via inclined/rotated ultraviolet (UV) lithography based on spatially controlled UV exposure doses. In comparison with other methods based on UV lithography, the present method can create microneedle structures with high scalability. When negative photoresist is exposed to inclined/rotated UV through circular mask patterns, a three-dimensional, needle-shaped distribution of the exposure dose forms in the irradiated region. Controlling the inclination angles and the exposure dose modifies the photo-polymerized portion of the photoresist, thus allowing the variation of the heights and contours of microneedles formed by using the same mask patterns. In an experimental study, the dimensions of the fabricated needles agreed well with the theoretical predictions for varying inclination angles and exposure doses. These results demonstrate that our theoretical approach can provide a simple route for fabricating microneedles with on-demand geometry. The fabricated microneedles can be used as solid microneedles or as a mold master for dissolving microneedles, thus simplifying the microneedle fabrication process. We envision that this method can improve fabrication accuracy and reduce fabrication cost and time, thereby facilitating the practical applications of microneedle-based drug delivery technology.

Highlights

Microneedles have been explored as a new class of effective transdermal drug delivery systems (DDSs) that offer minimally invasive, less painful, and self-administrable delivery[1,2,3,4]
Fabrication using integrated lens has been proposed for the creation of microneedle structures[10,11,12,13]. This integrated lens-based fabrication technique produces a large array of microneedles in a simple manner, but the technique is not scalable; modifying the microneedle geometry requires an entirely separate fabrication process to be conducted to change the lens geometry
We describe a theoretical approach to understanding the 3D distribution of the UV exposure dose and estimating the microstructure geometry

Summary

Introduction

Microneedles have been explored as a new class of effective transdermal drug delivery systems (DDSs) that offer minimally invasive, less painful, and self-administrable delivery[1,2,3,4]. Provided that the fabrication method is scalable, such a method could offer a means of achieving best-fit geometries for applications ranging from cosmetics to vaccinations. Because factors such as fabrication accuracy and cost are crucial for the use of microneedle-based DDS technology in practical applications, it is necessary to simplify fabrication to decrease fabrication cost and time while achieving sufficient fabrication accuracy. Fabrication using integrated lens has been proposed for the creation of microneedle structures[10,11,12,13] This integrated lens-based fabrication technique produces a large array of microneedles in a simple manner, but the technique is not scalable; modifying the microneedle geometry requires an entirely separate fabrication process to be conducted to change the lens geometry

Methods

Results

Conclusion