Abstract
Microneedles (MNs) have been extensively developed over the last two decades, and highly efficient drug delivery was demonstrated with their minimal invasiveness via a transdermal route. Recently, MNs have not only been applied to the skin but also to other tissues such as blood vessels, scleral tissue, and corneal tissue. In addition, the objective of the MN application has been diversified, ranging from drug delivery to wound closure and biosensing. However, since most MN fabrication methods are expensive and time-consuming, they are inappropriate to prototype MNs for various tissues that have different and complex anatomies. Although several drawing-based techniques have been introduced for rapid MN production, they fabricated MNs with limited shapes, such as thin MNs with wide bases. In this study, we propose a three-step thermal drawing for rapid, prototyping MNs that can have a variety of shapes and can be fabricated on curved surfaces. Based on the temperature control of polymer bridge formation during thermal drawing, the body profile and aspect ratios of MNs were conveniently controlled, and the effect of temperature control on the body profile of MNs was explained. Thermally drawn MNs with different shapes were fabricated both on flat and curved surfaces, and they were characterized in terms of their mechanical properties and insertion into vascular tissue to find an optimal shape for vascular tissue insertion.
Highlights
The first microneedle (MN) arrays were developed by microfabrication using dry reactive ion etching [1]
We propose a three-step thermal drawing technique to rapidly fabricate polymeric MNs that have a wide range of shapes on various surfaces
We focused on the real-time transitional phenomenon of a polymer bridge when the PLGA50/50 film was drawn by a micropillar (Figure 1B)
Summary
The first microneedle (MN) arrays were developed by microfabrication using dry reactive ion etching [1] This silicon MN array was inserted into human cadaver skin by making microincisions that act as drug delivery channels and increase the permeability of the human skin in vitro by up to four orders of magnitude. Since this first application of MN to human skin, which dramatically improved drug delivery efficiency, MNs have been extensively studied for transdermal drug delivery.
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