Controlling internal nanostructures of porous microspheres prepared via electrospraying

The focus of this work is to control and study internal nanostructures of electrosprayed polymer microspheres. In order to make the study easy, the microspheres were cut, and scanning electron microscopy coupled with image analysis software was employed to evaluate the size distributions and the internal nanostructures of microspheres. According to the observation and analysis results, three types of polyethersulfone porous microspheres (perfect sphere-shaped, red blood cell-shaped, and Chinese lantern-shaped) with a diameter ranging from 3 to 20 mu m were prepared via electrospraying technology. By controlling the process parameters, the porous microspheres with three kinds of internal nanostructures, namely, macrovoid internal nanostructure, sponge-pore internal nanostructure, and parallel internal macrovoid nanostructure were produced. The results demonstrate that the presence of some additive, such as polyethylene glycol and polyvinyl alcohol, can control the internal nanostructures of the electrosprayed microspheres effectively. The possible mechanism for the formation of internal nanostructures was also proposed.