Microfluidic Rapid Fabrication of Tunable Polyvinyl Alcohol Microspheres for Adsorption Applications.

Monodisperse polyvinyl alcohol (PVA) microspheres have been widely used for targeted drug delivery, embolization, and templates. However, the fast and facile fabrication of PVA microspheres with uniform size and internal structure and good sphericity remains a challenge. In this study, the PVA microspheres with uniformity in the size, shape, and internal structure were rapidly fabricated, using single-emulsion droplet templates by an on-chip approach. First, we designed a polydimethylsiloxane (PDMS) microfluidic chip integrated with three functional units, used for the droplet generation, mixing of reagents, and pre-curing of PVA microspheres, respectively. Then, we precisely controlled the generation of PVA aqueous droplets, mixing of reagents, and the gelation rate for the production of high-quality microspheres by adjusting the pH value, flow rate, and the channel structure. The prepared PVA microspheres are characterized with good sphericity, uniform internal structure, and narrow size distribution. The microspheres have good adsorption capacity and recyclability for small-molecule drugs, as demonstrated by the adsorption and desorption of methylene blue (MB). The adsorption behavior is well described by the pseudo-second-order model, and intraparticle diffusion is as fast as the external film diffusion.