Sequentially Controlled Deformations of Patterned Hydrogels into 3D Configurations with Multilevel Structures.

Sequential deformations of patterned hydrogels into 3D configurations with multilevel structures are reported, which are realized for the first time in self-shaping materials. The periodically patterned single-layer hydrogels with different polymers are fabricated by multi-step photolithography. After swelling in water, the expansion of compartmentalized high-swelling gels is constrained by the dispersed non-swelling gels, resulting in out-of-plane buckling with high cooperativity and thus forming alternating concave-convex configuration. When the dispersed non-swelling gels are partly replaced by thermoresponsive ones, the preformed overall flat, yet locally undulant, hydrogel deforms further into dome-, saddle-, or sandglass-like configurations at elevated temperature. As such, multilevel 3D structures can be achieved via prebuilt mechanical/geometric cues in a sequentially controlled manner. This conceptual design and sequential deformation of patterned hydrogels to form 3D configurations with multilevel structures should enrich the deformation/functioning modes of morphing materials and broaden their applications in diverse areas.