Single-Step Fabrication of Monodisperse TiO2 Hollow Spheres with Embedded Nanoparticles in Microfluidic Devices

A study was conducted to demonstrate single-step fabrication of hollow TiO2 (titania) microspheres with embedded functional nanoparticles in a coflow microfluidic device that was composed of two coaxial microcapillaries. Two glass microcapillaries were heated and pulled, along with a fine tip for the internal capillary and a narrow neck for the external one to fabricate the microfluidic device. The two glass capillaries were aligned manually by observing through a microscope and mounted the tip of the internal capillary in the necking region of the external capillary. The glass chip was also assembled by connecting with the inlet, outlet tubes, and sealing with optical adhesive. It was demonstrated that the reactivity of precursors needed to be controlled to employ microfluidic devices for fabricating titania microspheres, as sol-gel reaction of highly reactive metal alkoxide precursors occurred rigorously at the emulsion interface in contact with aqueous medium.