The microstruc-ture of chitosan film showed interconnective pores in the range of50–120 m and thin wall thickness less than 5 m without addingDMSO (Fig. 1a). Along with the ratio of DMSO increased, the poresize and wall thickness became smaller (Fig. 1b and c). Typically,the pore size dropped to 5 m and wall thickness was around sev-eral hundreds of nanometers in the chitosan film prepared withdioxane/DMSO ratio of 2.5:7.5 (Fig. 1c). Moreover, it had almostno pores in which only DMSO was added (Fig. 1d). Normally, soleacetic acid water solution was used as solvent to prepare chitosanscaffolds, the pore size and wall thickness of the prepared chitosanscaffolds were in the range of 100–500 m and 5–50 m, respec-tively (Jana, Florczyk, Leung, & Zhang, 2012; Madihally & Matthew,1999). In our study, both dioxane and DMSO were replaced byacetic acid water solution, the morphology of the chitosan film alsoshowed larger pore size (100–300 m) and thicker wall thickness(5–10 m) (Fig. 1e). These results indicated that the composition ofternary solvent system played an important role on the microstruc-ture of chitosan films. Acetic acid water solution with commonlyadopted concentration of 1% (v/v) was used to dissolve chitosan,dioxane was used to promote the formation of pores, and DMSOwas used to shrink the gelled samples to film