Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo 001-0021, Japan.
Faculty of Advanced Life Science, Hokkaido University, Sapporo 001-0021, Japan.
ACS Macro Lett. 2021 Jun 15;10(6):708-713. doi: 10.1021/acsmacrolett.1c00178. Epub 2021 May 20.
Biological tissues usually have complex superstructures and elaborated functionalities. However, creating superstructures in soft and wet hydrogels is challenging because of the absence of effective approaches to control the molecular orientation. Here we introduce a method to create superstructures in photonic hydrogels comprising lamellar bilayers intercalated in the cross-linked polymer network. The orientation of lamellar bilayers in the photonic gel, which are sensitive to shear, is modulated by applying a gradient shear field on the precursor solution using a customized rheometer. The difference in orientation of lamellar bilayers leads to swelling mismatch in the radial direction, endowing the disk-shape hydrogel with a macroscopic flower-like shape with a central dome and an edge petal, along with a bright photonic color. By characterization of the swelling anisotropy of the radial profile, the shear rate required for the unidirectional orientation of lamellar bilayers was extracted. Moreover, a delayed polymerization experiment was designed to measure the lifetime of aligned lamellar bilayers, which reveals the domain size of lamellar bilayers in the precursor solution. Furthermore, we also demonstrated that the hydrogel flowers could fade and rebloom reversibly in response to external stimuli. This work presents a strategy to develop superstructures in hydrogels and sheds light on designing biomimetic materials with intricately architectural superstructure.
生物组织通常具有复杂的超结构和精细的功能。然而，由于缺乏有效控制分子取向的方法，在柔软湿润的水凝胶中构建超结构具有挑战性。在这里，我们介绍了一种在包含层状双层的光子水凝胶中构建超结构的方法，这些层状双层嵌入在交联聚合物网络中。在光凝胶中，层状双层对剪切敏感，通过使用定制流变仪在前驱体溶液上施加梯度剪切场来调节层状双层的取向。层状双层取向的差异导致在径向方向上的溶胀失配，从而使盘状水凝胶具有宏观的花朵状形状，具有中央圆顶和边缘花瓣，并具有明亮的光子颜色。通过对径向轮廓的溶胀各向异性进行表征，提取了用于层状双层单向取向的剪切速率。此外，还设计了延迟聚合实验来测量取向层状双层的寿命，这揭示了前驱体溶液中层状双层的畴尺寸。此外，我们还证明了水凝胶花可以对外界刺激进行可逆的褪色和再显色。这项工作提出了一种在水凝胶中开发超结构的策略，并为设计具有复杂架构超结构的仿生材料提供了思路。
