Responsive Hydrogel Microstructures Fabrication using UCNs-incorporated Photocurable Nanoemulsion via Maskless Lithography

Abstract

In this study, we present a versatile approach to fabricating hydrogel micro-posts using an automated digital micromirror device (DMD)-based maskless lithography system with a photocurable nanoemulsion resin. Upconversion nanocrystals (UCNs), capable of transforming near-infrared light of lower energy into visible light of higher energy through upconversion, were embedded within a nanoemulsion matrix, offering a platform for diverse applications. We developed an effective and scalable technique for producing structured microgels by utilizing DMD maskless lithography, which provides quick and accurate patterning, and nanoemulsion technology, which makes it simple to mix materials with different properties without complex chemical processes. Furthermore, we demonstrated the potential of the photocurable UCN-embedded nanoemulsion system in two applications: an optical encryption system and a pH-sensitive degradation system. The reversible volume changes of the hydrogel microstructures enabled tunable luminescence intensity of UCNs, making it suitable for secure optical encryption. Additionally, we embedded biodegradable UCNs into the nanoemulsion to fabricate pH-sensitive hydrogel microstructures that exhibit controlled degradation under specific environmental conditions. This study highlights a novel and adaptable method for constructing UCN-integrated microstructures, paving the way for advanced optical security and responsive degradation systems.