Controllable fabrication of bioinspired pollen-like microparticles via solvent evaporation of polyvinyl alcohol (PVA)-stabilized microfluidic polymer microdroplets.

Shaping the polymeric materials into pollen-inspired microparticles with unique structural properties represent a promising area in drug delivery, environmental sensing, and biomaterials. This work reports a robust droplet microfluidic method for fabricating bioinspired pollen-like microparticles from polyvinyl alcohol (PVA) stabilized polymer-contained chloroform microdroplets followed by a solvent evaporation induced consolidation process. Monodisperse oil in water droplets containing dissolved polymer(s) in chloroform are initially generated in a glass capillary microfluidic device using an aqueous continuous phase containing PVA. The PVA provides robust droplet stability during the incubation/evaporation process by suppressing droplet coalescence and enabling reproducible interfacial conditions for morphology development. By systematically varying polymer type (homopolymer or copolymer), polymer concentration, PVA concentration (0.5% to 5.0% (w/v)), incubation temperature (5 °C to 30 °C), and the number of polymer components (one to four), we achieved precise control over particle morphology without requiring elaborately synthesized block copolymer or conjugate polymers. By leveraging these variables, comprehensive characterization through optical microimaging and scanning electron microscopy (SEM) are used to reveal distinct structural outcomes: single-component polymer droplets evolved into spherical microparticles with smooth, porous, or concave surfaces, whereas multi-component droplets yielded complex non-spherical and multi-compartment structures mimicking Bougainvillea, Canna, and Pinus pollen. This study elucidates the interplay between fabrication parameters and microparticle morphology properties, providing a versatile, synthesis-light strategy for innovatively designing functional microparticles with tunable bioinspired features from common polymers.