Water transport facilitated by carbon nanotubes enables a hygroresponsive actuator with negative hydrotaxis

 Hui Chen^‡a, Yuanhang Ge^‡a, Sunjie Ye ^b, Zhifeng Zhu ^a, Yingfeng Tu ^a, Denteng Ge ^c, Zhao Xu ^c, Wei Chen^*d and Xiaoming Yang ^*a,e（杨晓明）

^aState and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, Department of Polymer Science and Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, P. R. China

^bSchool of Physics and Astronomy, University of Leeds, LS2 9JT Leeds, UK

^cState Key Laboratory of Advanced Textile Materials and Manufacturing Technology (Zhejiang Sci-Tech University), Ministry of Education. State Key Laboratory for Modification of Chemical Fibers and Polymer Materials Institute of Functional Materials, Donghua University, Shanghai 201620, P. R. China

^dResearch Centre for Smart Wearable Technology, Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hong Kong 999077, P. R. China.

^eState Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, PR China

^‡These two authors contributed equally to this work

Nanoscale, 2020, 12, 6104--6110

Hygroresponsive actuators harness minor fluctuations in the ambient humidity to realize energy harvesting and conversion, thus they are of profound significance in the development of more energy-saving and sustainable systems. However, most of the existing hygroresponsive actuators are only adaptive to wet environments with limited moving directions and shape morphing modes. Therefore, it is highly imperative to develop a hygroresponsive actuator that works in both wet and dry environments. In this work, we present a bidirectional actuator responsive to both wet and dry stimuli. Our strategy relies on the introduction of carbon nanotubes to provide transport channels for water molecules. The actuation is enabled by the rapid transport of water in and out of the system driven by the moist/dry surroundings owing to the transport channels. The resultant actuator demonstrates reconfiguration and locomotion with turnover frequency F = 30 min⁻¹, coupled with the capability of lifting objects 6 times heavier and transporting cargos 63 times heavier than itself. Oscillations (24°) driven by dry air flow in a cantilever display a high frequency (2 Hz) and large amplitude. Furthermore, a touchless electronic device was constructed to output varying signals in response to humid and dry environments. Our work provides valuable guidance and implications for designing and constructing hygroresponsive actuators, and paves the way for next-generation robust autonomous devices to exploit energy from natural resources.

链接：https://pubs.rsc.org/en/content/articlelanding/2020/nr/d0nr00932f#!divAbstract