Figure 2
From: Orientation in multi-layer chitosan hydrogel: morphology, mechanism and design principle
Preparation of chitosan hydrogel by a single opening mold.
(a) Schematic diagram of preparation; (b) Digital photographs of gelation process at different reaction time. Solution and hydrogel were colored by bromothmol blue for visibility. In view of pH range, the blue part corresponded to hydrogel already formed while the yellow part corresponded to unreacted solution and the boundary indicated the hydrogel-solution interface.
