Hydrogel-based 3D fabrication of multiple replicas with varying sizes and materials from a single template via iterative shrinking.

3D printing technologies have been widely used for the rapid prototyping of 3D structures, but their application in a broader context has been hampered by their low printing throughput. For the same structures to be produced in a variety of sizes and materials, each must be printed separately, which increases time and cost. Replicating 3D-printed structures in a variety of sizes using a molding process with size-tunable molds could be a solution, but it has only been applied to simple structures, such as those with tapered or vertical profiles. This work demonstrates the generation of multiple replicas of varying sizes and materials from a single 3D-printed template with complex geometries by using molds made of stretchable hydrogel that shrink isotropically. We optimize hydrogel compositions to synthesize a hydrogel that is highly stretchable and shrinks isotropically in all directions. The high stretchability of this hydrogel allows for the removal of complex 3D-printed templates from hydrogel molds. The cavities of the hydrogel molds are then filled with polycaprolactone (PCL) and dried at 80 °C. As the hydrogel shrinks due to drying, the melted PCL fragments completely fill the cavities. The entire process can be repeated to produce multiple replicas in a variety of sizes and materials. Replicas that are one-tenth of the size of the original printed template can be produced. Finally, we demonstrate how our method can be used to reduce the size of interconnected geometries, which would be impossible to achieve using traditional molding processes.