Use of electrospinning to directly fabricate three-dimensional nanofiber stacks of cellulose acetate under high relative humidity condition

Unique structure-controllable three-dimensional (3D) nanofiber stacks of cellulose acetate (CA) were fabricated successfully by simply increasing relative humidity (RH) during the electrospinning process. It is found that once the RH exceeding 60 %, 3D flocculent nanofiber stacks would grow on the flat plate collector toward the needle tip without using special assisting apparatus or preparing special electrospinning solution. Compared with those obtained at low RH, the as-prepared nanofibers fabricated under high RH condition exhibited similar nanofiber diameter, density and porosity, and more importantly, 3D flocculent structures instead of typical two-dimensional (2D) electrospun non-woven mats, which would contribute to a significant improvement on the hydrophilicity. It is believed that rapid solidification of CA during the jet process and strong charge repulsion among CA nanofibers play important roles in the formation of 3D nanofibrous structure. Furthermore, these 3D flocculent nanofiber scaffolds exhibited better cytocompatibilities with human MG-63 cells than common 2D nanofibrous mats. Thus a facile and effective approach was presented to prepare 3D nanofiber stacks with tunable and reproducible properties for biodegradable scaffold applications.