Porous 3D Printable Hydrogels

Hydrogels are interconnected, polymeric networks filled with water. Their inherent responsiveness to different stimuli, including the presence of salt, solvents, or, depending on their composition, changes in pH or temperature, renders them attractive for actuation and delivery purposes. Yet, the limited diffusivity within hydrogels hampers an efficient exchange of reagents such as active ingredients or solutes. The diffusivity can be increased if pores are incorporated into hydrogels. However, these pores typically weaken hydrogels, preventing their use for load-bearing applications. This work reports a method to controllably introduce open pores with diameters of 10 s of nanometers into hydrogels whose mechanical properties are still remarkable, with compression moduli above 100 kPa. Importantly, these hydrogels can be 3D printed, thereby opening up possibilities to tune the pore size within hydrogels from the 10 s of nm up to the cm size range. This work leverages the 3D printability of this material to locally vary the degree of porosity while maintaining mechanical properties that enable facile handling of the integral samples. Thereby, this work introduces new opportunities to size-selectively infiltrate different substances at well-defined locations.