Figure 3. Self-healing properties of hydrogels.

(a–c) The effect of preparation parameters on the healing rate of the hydrogels embedded with (red bars) and without (light gray bars) the healing layer, respectively. (d–f) Optical images of the damaged hydrogel recorded as time after cut by a blade: (d) 0 s, (e) 5 s, and (f) 15 s. (g–j) A hydrogel column constructed from the connection of twelve hydrogel blocks alternating with six healing layers can be (g) held horizontally and (h) bended by hands, and a sample constructed by juxtaposing a healing layer between two hydrogel blocks exhibits extraordinary mechanical toughness: (i) before and (j) after stretching. Hydrogels with (red) and without (transparent) 0.05 wt% rhodamine B were prepared at [AAm]/[NVP] = 3:1 (mol/mol), BIS = 0 wt%, and O-CMC/monomer = 2.5% (w/w) and cut into small blocks prior to use.