Optimizing polymethyl methacrylate (PMMA)-based stretchable microneedle arrays by vat photopolymerization for efficient drug loading

Advancements in vat photopolymerization printing technology have enabled the fabrication of components with varying mechanical properties within a single print job. Using a digital light projector to cure photopolymer resins layer by layer, it allows the fabrication of parts with both flexibility and rigidity, in different regions. It simplifies the manufacturing process by eliminating the need for multiple steps. Specifically, for applications such as microneedles, printing onto a stretchable substrate is crucial compared to a rigid substrate, as it conforms better to the contours of the skin, ensuring more effective and comfortable drug delivery. However, a notable limitation of vat photopolymerization printing is the current lack of biocompatible materials, which restricts its application for microneedle fabrication. The challenge lies in developing materials that meet biocompatibility standards, while also being compatible with the printing technique and capable to achieve precise microscale structures. Therefore, we have developed an ultraviolet (UV)-curable polymethyl methacrylate (PMMA) suitable for the vat photopolymerization printing and the microneedles were designed to have a hollow side structure, enhancing drug loading efficiency. Comprehensive testing has been conducted, including durability test, drug loading efficiency, and skin penetration capability.