Chitosan fibrous 3D networks prepared by freeze drying

Nonwoven fabrics and structured particles prepared by electrohydrodynamic jetting have been attracting increasing attention in various research areas. Chitosan has been known as a poorly spinnable polymer, often electrospun using a mixed solution of polyethylene glycol. Herein, we report that a combination of electrospraying and subsequent freeze drying can produce chitosan fibrous 3D network structures from low concentration chitosan solutions, well below fiber forming concentrations. Nanoparticle suspensions of chitosan were first fabricated by a controlled electrospraying process and then freeze drying assembled the nanoparticles into fibrous networks. The formation of a columnar ice phase and subsequent drying produced chitosan fibrous structures of a few microns in diameter. The X-ray diffraction results and the surface morphologies of the fibers indicate a unique fiber formation mechanism of biaxial compression. This technique can prepare nonwoven fabrics from nanoparticles, which lead to novel opportunities in applications including tissue engineering, cell or drug delivery, and membranes.