Hydrogel self-healing test: the 8% and 17.5% (w/v) hydrogels (with and without a blue food dye) were prepared in the Eppendorf cap as mentioned previously. After their formation, the gels were cut in half using a blade. One of each halves were then pressed into each other in the same orientation as the cut. The combined hydrogels were observed at t=0, 3, 6 and 24 h to visualize the self-healing properties.