Hydrogel shape memory and actuating functionalities are heavily pursued and have found great potential in various application fields. However, their combination for more flexible and complicated morphing behaviors is still challenging. Herein, it is reported that by controlling the light-initiated polymerization of active hydrogel layers on shape memory hydrogel substrates, advanced morphing behaviors based on programmable hydrogel shapes and actuating trajectories are realized. The formation and photo-reduction-induced dissociation of Fe³⁺-carboxylate coordination endow the hydrogel substrates with the shape memory functionality. The photo-reduced Fe²⁺ ions can diffuse from the substrates into the monomer solutions to initiate the polymerization of the thermally responsive active layers, whose actuating temperatures and amplitudes can be facially tuned by controlling their thicknesses and compositions. One potential application, a shape-programmable 3D hook that can lift an object with a specific shape, is also unveiled. The demonstrated strategy is extendable to other hydrogel systems to realize more versatile and complicated actuating behaviors.

中文翻译：

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通过形状记忆基板上活性层的光导表面生长实现水凝胶的可编程热响应驱动

水凝胶的形状记忆和驱动功能受到大力追捧，并在各种应用领域发现了巨大的潜力。然而，将它们组合起来以实现更灵活和复杂的变形行为仍然具有挑战性。在此，据报道，通过控制形状记忆水凝胶基底上活性水凝胶层的光引发聚合，实现了基于可编程水凝胶形状和驱动轨迹的高级变形行为。^{Fe 3+} -羧酸配位的形成和光还原诱导的解离赋予水凝胶基材形状记忆功能。光还原的 Fe ²⁺离子可以从基板扩散到单体溶液中以引发热响应活性层的聚合，其启动温度和振幅可以通过控制它们的厚度和组成进行表面调整。一个潜在的应用，一个形状可编程的 3D 钩子，可以举起具有特定形状的物体，也被公开了。所展示的策略可扩展到其他水凝胶系统，以实现更通用和更复杂的驱动行为。