Experimental insight into the evolutionary mechanism of solid-to-hollow hydrogel.

We for the first time disclose the evolutionary mechanism of solid-to-hollow sodium alginate (SA) hydrogel in an aqueous solution of Cu2+, H2O2 and Tris-HCl elements, where the oxidative degradation and gas bubble assistance result in the hollow structures. This provides a promising concept or method basis for the preparation of hollow hydrogels with sophisticated geometries.