DLP 3D printed hydrogels with hierarchical structures post-programmed by lyophilization and ionic locking

Porous hydrogels have been intensively used in energy conversion and storage, catalysis, separation, and biomedical applications. Controlling the porosity of these materials over multiple length scales brings about new functionalities and higher efficiency but is a challenge using the current manufacturing methods. Herein we developed a post-programming method to lock the lyophilized pores of 3D printed hydrogels as an experimental platform towards hierarchically structured pores. 3D printing endows the hydrogels with arbitrary 3D geometries and controllable pores at the millimeter length scale. Lyophilization and ionic crosslinking of the as-printed hydrogel networks are conducted as a post-programming process which results in pores at micrometer length scales beyond the printing resolution. Utilizing this combined manufacturing technology, 3D hydrogel lattices with tunable porosities and mechanical properties can be created, which are further exploited for efficient solar vapor generation.