Lyu Dengping, Xu Wei, Zhou Nansen, Duan Wendi, Wang Zhisheng, Mu Yijiang, Zhou Renjie, Wang Yufeng
Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China.
Department of Biomedical Engineering, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China.
Sci Adv. 2023 Jun 30;9(26):eadh2250. doi: 10.1126/sciadv.adh2250.
Soft-and-hard hybrid structures are ubiquitous in biological systems and have inspired the design of man-made mechanical devices, actuators, and robots. The realization of these structures, however, has been challenging at microscale, where material integration and actuation become exceedingly less practical. Here, through simple colloidal assembly, we create microscale superstructures consisting of soft and hard materials, which, serving as microactuators, have thermoresponsive shape-transforming properties. In this case, anisotropic metal-organic framework (MOF) particles as the hard components are integrated with liquid droplets, forming spine-mimicking colloidal chains via valence-limited assembly. The chains, with alternating soft and hard segments, are referred to as MicroSpine and can reversibly change shape, switching between straight and curved states through a thermoresponsive swelling/deswelling mechanism. By solidification of the liquid parts within a chain with prescribed patterns, we design various chain morphologies, such as "colloidal arms," with controlled actuating behaviors. The chains are further used to build colloidal capsules, which encapsulate and release guests by the temperature-programmed actuation.
软硬混合结构在生物系统中无处不在，并启发了人造机械设备、致动器和机器人的设计。然而，在微观尺度上实现这些结构一直具有挑战性，因为在该尺度下材料集成和驱动变得极不实用。在这里，通过简单的胶体组装，我们创建了由软材料和硬材料组成的微观超结构，这些超结构作为微致动器，具有热响应形状转变特性。在这种情况下，作为硬组分的各向异性金属有机框架（MOF）颗粒与液滴集成在一起，通过价键受限组装形成模仿脊柱的胶体链。这些链具有交替的软硬段，被称为微脊柱（MicroSpine），并且可以通过热响应溶胀/消肿机制在直态和弯曲态之间可逆地改变形状，实现形状切换。通过以规定模式固化链内的液体部分，我们设计了各种具有可控驱动行为的链形态，如“胶体臂”。这些链进一步用于构建胶体胶囊，通过程序升温驱动来封装和释放客体。
