3.3.2. SEM observation
Material properties are always linked to the structure at all lev- els which is the result of chemical composition, arrangement, and processing conditions (Ciechanska, 2004). The surface and inner matrix of BC sheets were evaluated through SEM analysis, as shown in Fig. 6, see Supplementary figure. The microstructure of the bacterial cellulose produced under the optimal conditions selected in this work is similar to the one previously presented in the literature (Klemm et al., 2001). The micrograph of the cross section shows that the micro-fibrils of BC membranes are randomly and loosely arranged with plenty of spaces among them (Fig. 6A, see Supplementary figure). This arrangement of fibrils results in the formation of pores with different diameters on the surface (Fig. 6B, see Supplementary figure) and through the entire matrix of the BC sheets (Fig. 6C and D, see Supplementary figure). In this microstructure the water molecules can be sandwiched between the pores of the thick fibrils, and these fibrils can act as a shield for water molecules. Hence, these fibrils display high water holding capacity, slow water release ability and quick water absorbing ability.