Microfluidics-based preparation of thermosensitive monodispersed silica-PNIPAM hybrid particles with core–shell or snowman morphologies

Abstract

Organic–inorganic hybrid particles have unique properties derived from the combination of their constituents and morphology, thereby enabling them to perform crucial functions in applications across the biomedicine, pharmaceutical, cosmetic, materials science, and engineering industries. This paper reports a method for preparing monodispersed hybrid particles comprising silica and thermosensitive poly(N-isopropylacrylamide) (PNIPAM) hydrogel particles with core–shell or snowman morphologies using a microfluidic device. Here, monodispersed droplets of sodium silicate solution are generated using a flow-focusing microfluidic device. When sodium hydrogen carbonate (NaHCO₃) and N-isopropylacrylamide (NIPAM) are simultaneously transferred to the droplets, sodium silicate reacts with NaHCO₃ to form core–shell structures, wherein silica-rich droplets are generated inside the NIPAM-rich droplets. The droplets are subsequently irradiated with ultraviolet (UV) light to yield monodispersed silica-PNIPAM hydrogel core–shell particles. However, when only NaHCO₃ is transferred to the sodium-silicate solution droplets, a snowman-like structure comprising silica-rich and water-rich droplets is formed. Therefore, NIPAM can be transferred to water-rich droplets and photopolymerized via UV light irradiation to obtain monodispersed snowman-like silica-PNIPAM hydrogel hybrid particles. Furthermore, the PNIPAM hydrogel hybrid-particle size can be easily altered by changing the temperature to approximately the human body temperature.