Controllable Fabrication of Monodisperse Poly(vinyl alcohol) Microspheres with Droplet Microfluidics for Embolization

A novel strategy based on droplet microfluidics is developed for facile fabrication of monodisperse poly(vinyl alcohol) (PVA) microspheres with controllable sizes and elastic properties for embolization. Monodisperse emulsion droplets are fabricated as templates by dissolving PVA and boric acid in the aqueous disperse phase, and chemical cross-linking between PVA and boric acid inside droplet templates is triggered by adding NaOH into the downstream receiving solution. The cross-linking speed and degree between PVA and boric acid inside droplet templates can be controlled by adjusting the NaOH concentration, height, and rotating speed of the receiving solution. The sizes of droplet templates and resultant cross-linked PVA microspheres can be precisely controlled by adjusting the characteristic dimensions of the microfluidic device as well as the flow rates of disperse and continuous phases. Moreover, the elastic, swelling, and drug-loading properties of PVA microspheres can be controllably regulated by adjusting the ratio of PVA to boric acid in the disperse phase. With an in vitro chip, excellent embolization performances of the fabricated PVA microspheres are visually demonstrated. The proposed strategy provides a facile and efficient route for fabricating monodisperse PVA microspheres with a controllable size and elastic, swelling, drug-loading, and drug-release properties, which are highly desired for applications in embolization therapy.