Piezoelectrically-driven production of sub 10 micrometer smart microgels

It is highly desirable to prepare crosslinked microgels whose diameters are comparable to that of a single mammalian cell (i.e., ~10 μm) with desired monomers for potential biomedical applications. In this study, we have prepared a large number of stimuli-responsive poly(N-isopropylacrylamide) microgels through photo-polymerization in oil of aqueous monomer droplets ejected from a microdroplet generator. The crosslinked microgels as small as 8 μm in diameter could be prepared with a uniform shape and narrow size distribution, and their size could be controlled by adjusting the applied voltages. The size of microgels with LCST behavior was shown to be reduced to ~5.7 μm with increases in the temperature. Furthermore, the functional monomers, such as fluorescent moieties and photothermal graphene oxide, could be incorporated within the polymer matrices, which introduces the possibility for practical applications such as on-demand drug release systems, tissue engineering, and soft actuators of these microgels.