CAS Key Laboratory of Bio-Based Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences , Songling Road 189, Qingdao 266101, P. R. China.
University of Chinese Academy of Sciences , 19A Yuquan Road, Beijing 100049, P. R. China.
ACS Appl Mater Interfaces. 2017 Sep 20;9(37):32280-32289. doi: 10.1021/acsami.7b10348. Epub 2017 Sep 5.
Macroscopic soft actuation is intrinsic to living organisms in nature, including slow deformation (e.g., contraction, bending, twisting, and curling) of plants motivated by microscopic swelling and shrinking of cells, and rapid motion of animals (e.g., deformation of jellyfish) motivated by cooperative nanoscale movement of motor proteins. These actuation behaviors, with an exceptional combination of tunable speed and programmable deformation direction, inspire us to design artificial soft actuators for broad applications in artificial muscles, nanofabrication, chemical valves, microlenses, soft robotics, etc. However, so far artificial soft actuators have been typically produced on the basis of poly(N-isopropylacrylamide) (PNiPAM), whose deformation is motived by volumetric shrinkage and swelling in analogue to plant cells, and exhibits sluggish actuation kinetics. In this study, alginate-exfoliated WS nanosheets were incorporated into ice-template-polymerized PNiPAM hydrogels with the cellular microstructures which mimic plant cells, yet the prompt steerable actuation of animals. Because of the nanosheet-reinforced pore walls formed in situ in freezing polymerization and reasonable hierarchical water channels, this cellular hybrid hydrogel achieves super deformation speed (on the order of magnitude of 10° s), controllable deformation direction, and high near-infrared light responsiveness, offering an unprecedented platform of artificial muscles for various soft robotics and devices (e.g., rotator, microvalve, aquatic swimmer, and water-lifting filter).
宏观软致动是自然界中生物体固有的特性，包括植物的缓慢变形（如收缩、弯曲、扭曲和卷曲），这是由细胞的微观膨胀和收缩驱动的，以及动物的快速运动（如水母的变形），这是由运动蛋白的协同纳米尺度运动驱动的。这些致动行为具有可调节速度和可编程变形方向的独特组合，激发了我们设计用于广泛应用的人工软致动器，如人工肌肉、纳米制造、化学阀门、微透镜、软机器人等。然而，到目前为止，人工软致动器通常是基于聚（N-异丙基丙烯酰胺）（PNiPAM）生产的，其变形是通过类似植物细胞的体积收缩和膨胀来驱动的，并且表现出迟缓的致动动力学。在这项研究中，将海藻酸钠剥离的 WS 纳米片掺入到具有类似于植物细胞的细胞微观结构的冰模板聚合 PNiPAM 水凝胶中，然而却能实现动物的快速可控致动。由于在冷冻聚合过程中形成的纳米片增强的孔壁和合理的分级水通道，这种细胞混合水凝胶实现了超变形速度（量级为 10° s）、可控的变形方向和高近红外光响应性，为各种软机器人和设备（如旋转器、微阀、水生游泳者和水提升过滤器）提供了一个前所未有的人工肌肉平台。
