Programming the Shape Transformation of a Composite Hydrogel Sheet via Erasable and Rewritable Nanoparticle Patterns.

Hydrogels with shapes that can be adapted to their environment have attracted great attention from both academia and industry. We report herein a new and robust strategy to reprogram the light-induced shape transformation of a thermoresponsive composite hydrogel sheet with erasable and rewritable patterns of iron oxide nanoparticles as photothermal agents. Numerous distinct and reversible shape transformations are achieved from a single hydrogel sheet by repeatably writing in the sheet with different nanoparticle patterns. The shape transformations were verified by finite element modeling. The present strategy is simple, fast, and efficient in reprogramming the shape change of the thermoresponsive hydrogel material. The composite hydrogel sheet may find applications in soft robotics, tissue engineering, and controlled release.