A Practical Microfluidic Device for Synthesis of Purified Monodisperse Micro-Alginate Beads (MABs) as Microcarriers of Gold Nanoparticles. We developed a microfluidic device for encapsulating gold nanoparticles in Micro-Alginate Beads (MABs). The size and the gap of the monodisperse alginate droplets were successfully controlled by adjusting the relative "oil/sample" flow rate ratio. Droplets reacted with calcium ion at the interface between oil phase and aqueous phase so that MABs precipitated spontaneously and undergone complete gelation. Purified MABs were successfully observed by fluorescence microscopy.